1. The church at Antioch is vibrant. Look at its prophets! Agabas predicts a severe famine that will sweep the Roman Empire and, apparently as in the days of Joseph in Egypt, they get ready. Acts tells us that the word, "Christian," first sprang up in Antioch. Before that they seem to have been called followers of "the Way."
Look at the missional mindset of the Christians at Antioch! This famine seems to have happened around AD44, during the reign of Claudius. Paul and Barnabas carry some food relief down to Jerusalem from the church at Antioch. Interestingly, Paul doesn't mention this trip to Jerusalem in Galatians 1. So if Paul's lost years were from around AD36 to, say, AD43.
The leaders of the Jerusalem church were called "the elders." It's interesting to ask whether this group actually included the disciples who were still in town, since these leaders probably were actually older. While local assemblies probably were led in part by elders, the assemblies in Jerusalem seemed to have a group of elder-leaders who were not only over all the house churches in Jerusalem but may have thought of themselves as the ultimate leaders of the whole Jesus movement, a kind of Christian version of the Sanhedrin.
2. Acts 12 is a tale of persecution and justice. In the first half of the chapter, Herod Agrippa I persecutes the church. In the second half, his intestines explode. This is the Herod that was friends of the Emperor Caligula and who apparently interceded for the Jewish people when Caligula tried to set up a statue of himself in the temple around AD39.
It is also the Herod whose pomp when visiting Alexandria, Egypt, led to some riots against the Jews there around AD38. Philo ended up taking a delegation to Rome over that one, and it eventually led to a downgrading of the Jews' position in the city. The emperor Claudius tells them to be happy with who they are--which isn't Roman citizens.
This Herod puts James, the brother of John, the son of Zebedee, to death. My hunch is that this is the brother of John, the author of Revelation. Perhaps he was as apocalyptic as the book of Revelation. We don't know anything about the circumstances leading up to his arrest and death. He may have been quite zealous, but unfortunately is largely forgotten to time and history. He is the first of the apostles to die.
3. Herod goes for Peter next. This story is almost comical. Peter thinks he's having a vision. "Boy, this is nice. I'm escaping in this dream. I wonder what this means." Of course it turns out not to be a dream.
He goes to Mark's house--the John Mark who will go with Paul and Barnabas on their first missionary journey to Cyprus. This is the Mark that tradition suggests wrote the Gospel of Mark (although Mark itself does not say so). His family must have had some wealth. They have a servant and a big enough house for lots of people to gather. Theoretically, this might explain how Mark could know Greek and why he was none too pleased about backpacking through Asia Minor.
The servant Rhoda is so excited she doesn't let Peter in. They're praying for him but apparently not with a lot of faith. "Lord, help Peter not to suffer too much tomorrow when they kill him."
"He's at the door!"
"Go away Rhoda... We're praying for Peter."
She finally convinces them and they think, "They've already killed him. It's his ghost/angel." Interesting window into how Luke thought about the intermediate state. He apparently thinks a person becomes an angel of sorts at death (cf. Acts 23:8), maybe an intermediate embodied state before the final resurrection. It would be different than a spirit in that sense because it would involve a body.
4. Note that this time, when Peter is the actual target of persecution, he leaves town. This supports the idea that he was not the target when Paul was persecuting the Greek-speaking Christians of Jerusalem in Acts 8. Note also that James is not at the prayer meeting, possibly implying that he was part of another house church in Jerusalem.
5. The moral of Herod's story is, "If someone says you're like a god, deny, deny, deny!" Josephus tells about his death as well.