"When they saw the courage of Peter and John
and realized that they were unschooled, ordinary men,
they were astonished and they took note that that these
men had been with Jesus."
At the time Luke wrote this, Jesus had been crucified, already returned to heaven, and Pentecost was over,* yet the rulers, elders, and teachers of the law noticed that Peter and John had been with Jesus. Had Peter and John already figured out how to spend time alone with Jesus praying in spirit and truth (John 4:23-24)? He hadn't been with them (physically) in a while. The answer is yes, because when we back up to verse 8 in this chapter, Acts 4, Peter answered the rulers questions filled with the Holy Spirit.
Since Pentecost 2009 years ago, praying works the same way for Peter and John as it does for us. We cannot speak in the power of the Holy Spirit without spending time alone with Jesus listening to him through his word. The only difference is that Peter, John, and others were working on writing the word of God, but we have the complete and perfect word of God in our hands between a leather cover. We have the privilege of knowing the whole story, even the end that has not happened yet.
The verse bolded above makes me ask myself--Who is taking note of me? Does how I act prove who I hang with? I hope and pray people around me can tell I spend time alone with Jesus. I have some bad days, but for the most part, I desire for those God puts in my path to have their notepads ready and jot down "Susan has been with Jesus!" Because when it comes down to it, everything good I do is his idea, anyway.
*Jesus was crucified during Passover, after he rose he stayed on earth for 40 more days (Acts 1:3). Pentecost occurred 50 days after Passover.