Does the book of Acts intend to tell us a historical narrative, or does Luke tell us how we should be living? In other terms, is it just descriptive, or is it also prescriptive?
One approach is that we should follow what Acts says – or follow it more confidently – only when its narrative is reinforced by specific propositional teaching, that is, declarative statements from the gospels or epistles. If we cannot, then it might be appropriate to question whether the apostles were making good decisions.
On the other hand, Craig Keener leans toward the “prescriptive” viewpoint, stating that Hellenistic and Jewish histories of the period were not simply records of what happened, but models for the reader to follow: “it should not surprise us that Luke is explicit in presenting his primary protagonists as models for virtue” and also to show how God providentially worked in history.  I broadly agree with him that the book of Acts is a gift of the Spirit to tell us the truth about us, the church universal, not just the facts of the past.
I would say that: Rule #1 is, by default, Acts calls us to listen to what we should be doing, and Rule #2 is, follow Rule #1 up to the point where the narrator clearly shows disapproval. Its default is prescriptive, unless you can prove different, the actions of its participants have the Spirit’s seal of approval.
One easy example is when Acts describes, various times, the conversion of Cornelius in Acts 11:11-12.
At that very moment three men, sent to me from Caesarea, arrived at the house where we were. The Spirit told me to go with them and not to make a distinction between them and us.
And Peter’s critics had to conclude in 11:18, “When they heard these things they fell silent. And they glorified God, saying, ‘Then to the Gentiles also God has granted repentance that leads to life.’” There is confirmation after confirmation (special revelations, Scriptural backing, sanctified reasoning) that this was God’s will. But this is only told the reader by means of narrative, not “propositional truth”.
One negative example, a clear target of divine censure, is Simon Magus in Acts 8:18-19:
Now when Simon saw that the Spirit was given through the laying on of the apostles’ hands, he offered them money, saying, “Give me also this power so that anyone on whom I lay my hands may receive the Holy Spirit.”
Or better, we should positively frame it, that Acts does gives God’s seal of approval on Peter’s action in 8:20-21:
But Peter said to him, “May your silver perish with you, because you thought you could obtain God’s gift with money! You have no part or share in this, for your heart is not right before God.”
(Like most Christians in Latin America, I have heard a section of a sermon by Prosperity Gospeler Cash Luna. Grossly enough, he says that it was Simon Magus who was right to offer money in order to receive a special anointing of the Spirit, and that Peter was wrong: according to Cash, Peter should have realized that you can get the Spirit’s power if you give money to an anointed ministry – Cash’s, by implication. But, let’s keep to the sensible cases and examine a text that is less clear-cut).
TEST CASE: WERE THE APOSTLES IN THE RIGHT WHEN THEY CHOSE MATTHIAS TO BE THE TWELFTH APOSTLE IN PLACE OF JUDAS ISCARIOT?
Standard Interpretation: the apostles carried out God’s will by appointing Matthias
Alternative Interpretation: the apostles made a merely human decision, rushing in to make Matthias the twelfth apostle, when they should have patiently waited until Saul was converted to replace Judas (some say they should have appointed James the brother of the Lord). 
The text of Acts 1 appear to contain clear markers of the Spirit’s approval of the apostles’ actions, and zero indication that they erred:
- The apostles had just days earlier heard exactly how the messianic Scriptures were fulfilled (Luke 24:44-49, which is just one chapter prior to Acts 1 in Luke’s two-volume work); Luke 22:30 also contains Jesus’ prediction that, despite Judas’ defection, there would be twelve people to judge the twelve tribes of Israel); part of that messianic narrative was the betrayal of Jesus by his friend; Acts 1 implies that they knew that it was proper to interpret Psalm 69:25 and 109:8 to mean that they should choose a replacement for Judas, and in that moment of time; that is, they knew that this action was biblical;
- The apostles prayed before choosing Matthias;
- They cast lots, using the ancient biblical method to determine the selection of leaders (e.g., 1 Chron 24:31). This was asking God for his guidance by a divine oracle; it doesn’t mean they voted.
Again, my principle is that, by default, what Acts presents to us is to be considered wise and godly Christian action, and enjoys God’s approval, provided that the author does not signal to the reader that it should not. And in this case, the author of Acts piles on evidence that Matthias was an apostle and one of the Twelve, as in these passages.
2:37 “Peter and the other apostles” (acc to Acts, this means Peter plus the eleven, including Matthias)
2:42 “They devoted themselves to the apostles’ teaching and fellowship” (implying Matthias taught them)
2:43 “many wonders and signs were being done by the apostles” (Matthias and his colleagues perform apostolic miracles)
4:33 “With great power the apostles gave their testimony to the resurrection of the Lord Jesus” (Matthias does apostolic miracles and proclaims the resurrection, which he witnessed); similarly,
5:12 “Now many signs and wonders were done among the people through the apostles”
5:18 “arrested the apostles and put them in the public prison” (just eleven men? No, all twelve!)
5:40 “when they had called in the apostles, they had them flogged” (Matthias got flogged! He got no free pass for being a fake apostle)
6:2 “And the twelve called together the whole community” (all twelve, including Matthias); also, 6:6 “They had these men stand before the apostles, who prayed and laid their hands on them”
8:1 “all except the apostles were scattered throughout the countryside of Judea and Samaria” (Matthias wasn’t scattered)
8:14 “Now when the apostles at Jerusalem heard that Samaria had accepted the word of God, they sent Peter and John to them” (Matthias and nine other apostles sent Peter and John!)
All of these, by strong insinuation, reinforce that according to Acts, Matthias belonged on the roster of the Twelve. Also: Matthias is still called an apostle, even after Saul was commissioned by Christ:
9:27 “But Barnabas took [Saul], brought him to the apostles, and described for them how on the road he had seen the Lord.” In other words, Saul meets Matthias, whom Acts continues to confirm as an apostle. Saul’s conversion doesn’t de-activate Matthias’s apostleship. And if we want the apostle Paul’s word on the matter, he obliquely includes Matthias in the list of the twelve apostles, affirming with the apostles in Acts 1 that Matthias was a witness to the resurrection: 1 Cor 15:5 – “he appeared to Cephas, then to the twelve” [which must include Matthias, who was an eyewitness of the resurrection, according to Acts 1:21.]
In later references: Irenaeus accepts him as the twelfth apostle in Against heresies 2.20.1; Hippolytus agrees, saying that he was one of the 70 disciples in Luke 10:1, and that he died in Jerusalem (ANF 5.525); other tradition says that he worked and was martyred in Ethiopia. His apostleship is affirmed by Eusebius, History of the Church 1.12.3; Clement of Alexandria, Origen, Augustine, Chrysostom in his homily on Acts. There was a gnostic Gospel of Matthias, another document called the Traditions of Matthias, and also an Acts of Andrew and Matthias (ANF 8). The reference to twelve apostles in Revelation 21:14 appears to refer to the Twelve-including-Matthias: “And the wall of the city had twelve foundations, and on them were the twelve names of the twelve apostles of the Lamb.”
But what about the apostle Paul?
First, in no place does Acts call Paul the twelfth apostle; in fact, he is called an apostle only when Barnabas is also so named (Acts 14:4, 14). In his letters, Paul claims to be an apostle, but never one of the Twelve. He was especially chosen, but he also applies the term “apostle” to James (Gal 1:19), and to other pioneer missionaries – Junia (a woman, Rom 16:7), Andronicus (probably her husband, same text), Silvanus (1 Thess 2:6).
Conclusion: the author of Acts does not simply describe what the apostles did in Acts 1; he approves, and affirms that Matthias was God’s choice to replace Judas Iscariot.
There are other texts that require hermeneutical finesse. Two of them are:
Acts 2 records that “all who believed were together and had all things in common. And they were selling their possessions and belongings and distributing the proceeds to all, as any had need” (2:44-45). Especially during the Cold War, when any whiff of socialism was carefully excised from the Bible’s message, I used to hear, first, that this doesn’t really teach a socialist government system (true); but also that it was a mistake on the part of the believers, because communal sharing is unpractical, and it inexorably led to economic implosion and poverty that the gentile churches were compelled to alleviate. 
In our times, the weird and wacky Conservative Bible Project neatly cuts out the idea from Acts, justifying itself by pointing out that “had all things in common” is “commonly misread as socialistic nowadays, but doesn’t refer to material” [sic]. Instead of sharing goods, they render it “Everyone who believed was together and shared values, faith, and the truth”. They offer no proof from the Greek text. They retranslate – rather, mistranslate; well, let’s say, misparaphrase – the parallel passage in Acts 4:34-35 as well.
Again, nothing in Acts indicates that that is the way to read the narrative. Everything indicates that it receives God’s seal of approval, and that the Spirit did not warn them away from sharing their goods.
PAUL’S TEMPLE SACRIFICE
More subtle but worth our notice is the action of Paul in Acts 21:26, “Then Paul took the men, and the next day he purified himself along with them and went into the temple, giving notice when the days of purification would be fulfilled and the offering presented for each one of them.” One writer argues that, “Nothing in the text suggests that this was a wise move. It doesn’t lead to Jewish evangelism, and in fact, a lynch mob stops this event from happening…God seems to have interrupted this event, perhaps showing that Paul shouldn’t have put himself in this situation in the first place.” 
Maybe, but I find it too clever by half. Nowhere does Acts express disapproval of his action; and besides, Acts (and Paul in Romans 15:31) had already given plenty of warning that Paul was walking into a highly perilous situation, that is, that Paul’s action or inaction with the sacrifice was not the cause. It was Paul’s mere presence in the temple, and the false charge that he had taken gentiles into the inner court, that sparked the riot.
(Another topic would be whether Paul took a wrong turn in his Athens speech, a strategy he regretted and corrected at his next stop, in Corinth. But that merits a page of it’s own.)
While we cannot pull aside the curtain on all the events in Acts, we might also accept that there are events that are not prescriptive in the details: should there always be seven deacons, should they always be males, should they always be Hellenistic Jews?; should we baptize new believers instantly, as with the Ethiopian in Acts 8?; should we pray at set hours, as in Acts 3:1?; should all evangelism begin in Diaspora synagogues? were Paul and Barnabas at fault when they split up?
But as a rule, let’s give the story of Acts the benefit of the doubt.
 See Craig S. Keener, Acts: an Exegetical Commentary, 1:157.
 See E. M. Blaiklock, The Acts of the Apostles: An Historical Commentary (London: Tyndale, 1959), p. 53.
 Blaiklock again, p. 69: “…the poverty of the Jerusalem church, which later called for world-wide charity, may have been occasioned by this over-hasty dissipation of capital. Likewise, E. F. Harrison, Interpreting Acts: the Expanding Church.
“The Book of Acts: Do the apostles always do right?” by Gary S. Shogren, Profesor de Nuevo Testamento, Seminario ESEPA, San José, Costa Rica