My church follows this format:
If it’s the Sunday morning service, Sunday school is offered, where you go to a class. For kids, it’s all basically assigned to you. For adults, there are often different ones. If you aren’t a member, you’re not really expected to show up to these, unless someone invited you. How exactly the class goes varies by the teacher, but usually it involves taking attendance, asking for prayer requests, praying, and then teaching a spiritual lesson of some sort, often from a book or program.
Main service: You arive within 15 minutes of the starting time, where there will likely be announcements on the back wall, as well as a paper bulletin with announcements. Eventually, the pastor will come forth and welcome people, and say stuff like “say hi to your neighbor,” have a prayer, and hand it over to the worship leader. He will then direct the musicians to start the first song on their list, and the lyrics will be displayed on the back wall. If it is a hymn, the leader may also tell you to open to a particular page in the hymnal if you’d rather do that.
There will be a few such songs, usually staying upbeat, and usually older songs first. Then the worship leader will turn it back over to the pastor, who will ask for prayer requests, where people can mention things they need prayer for. Sometimes there will also be testimonials, where you praise God for the good things. After that, the pastor will ask if there are any “unspoken” requests, and people will raise their hands, and then he’ll lead us in a prayer about all of them.
After the prayer, he’ll turn it back over to the worship leader, who will then have another set of songs, usually songs, especially the last song. Either the worship leader or the pastor will then invite the ushers to come forth with the collection plates for an offering, and there will be a prayer before they start collecting. While the offering is being collected, there will often be someone from the congregation who will do a special song or other performance. If not, then the musicians and worship team (basically backup singers) will fill in with a song.
Then it’s time for the sermon. Either the pastor will preach, or they’ll announce the guest speaker. The sermon is basically a speech based on a religious concept, and usually begins with a portion of scripture. The congregtation will be told the scriptures chapter and verse, and can turn to them in their bibles (now often electronic). Usually the screen will function like a Powerpoint presentation, and will have the scripture there as well.
The exact nature of the sermon varies, but usually it seems to be about taking what happened and either literally or figuratively applying it to our lives, discussing the difficulties in doing so, and stuff like that. Usually there will be other scripture references to back it up.
The sermon often ends in an altar call. This will be a call to come forward and have people pray with you individually over the issues mentioned in the sermon. Sometimes, the altar call will instead be about salvation, and asking if God has pricked their heart and they want to convert to Christianity. And sometimes both. Usually after a bit, people will be invited to come up for any other reason they might want to be prayed for. During this time the musicians may come back and play some music, or there may be prerecorded music played.
After some time of praying, the pastor will usually come back after the altars have mostly cleared and dismiss us and provide an exhortation to keep on doing what we need to do, and end with a prayer. Sometimes, the altar remains full, and instead we get what I call a half-dismissal, where the pastor comes back and gives the exhortation only. And sometimes, the only sign that you can leave is when they switch from live to prerecorded music. (Though, technically, it’s generally considered okay to leave after 10 minutes of altar time.)
Assuming a proper dismissal, the pastor will usually wait near the doors in the back and greet people as they leave. And usually there’s a lot of talking with people in the church itself or in the foyer.
If there is an activity after the service that is open to all, the dismissal will have mentioned that, and you meet in the fellowship hall. This is most common for morning services, and the activity usually includes lunch.