Contemplating when to go to yard sales is not an easy choice. Some have their luck in the early morning when not much is going on. Others may have a lot of success in the afternoon. Here is my very quick thoughts on this. I have been doing local yard sales the last seven, eight years. I have found some great video games, films, tv shows.
If you want to do some good damage, try to get to places in the morning. Not too early where's there only a few houses selling things, but not to the point where it is already crowded. Go from one side of town to the other. Maybe go through a few streets as you go down the main road. When you get to the end, start attacking the streets. You might still be able to get some stuff if you check yard sales, even in the afternoon. You never know what you are going to find. It might be for a good price, especially if you get NES games for very cheap.
If people get to stuff before you do, you might get frustrated. Don't act rude in public. It's not a big deal unless it's for something that you can't find anywhere else if it's that important to you. Don't get overboard with buying everything. Budget yourself how much you want to spend and if you reach a limit, consider it a day.
Those are just some of my approaches to yard sales. I don't know if it will work for others, but you can have some good fun finding some good stuff, eating maybe some chicken or burgers, too. Just stay calm and you can have a good experience at yard sales.