Not Having a Ball
Ever since the weather got nice, the neighbor kids who live across the street from me have been playing raucous games of soccer in the street in front of my house. The ball hits my window all the time, and I've even found the kids standing on my stoop as part of the game. It's a huge nuisance, plus I'm afraid someone or something is going to get hurt. What's the most effective way to get the games to stop?
Not Having a Ball
On the one hand, kids will be kids. On the other hand, this is a total violation of your space. Those two viewpoints are going to be in tension while you deal with this, no matter what. You don't want to be that curmudgeon across the street, and you also don't want a broken window. While you're not these kids' parent and not responsible for their welfare, you can still take a parental approach and either use incentives or punishment.
The best option would be to find a reason for them to believe that not playing on your stoop is far preferable to playing there. Depending on their ages, you might be able to convince them of this by giving them candy to make them go away on a regular basis. You could also attempt to orchestrate some sort of rewards program where they can earn something they really want for leaving you the heck alone. For example, a whole week of not playing in the street gets them a new ball, or something. These things will cost you, but it's a small price to pay relative to house damage and the aggravation you're experiencing now. Plus, you'll seem like a good guy instead of a jerk.
Before you offer them anything, though, it's a good idea to consult with their parents who, in an ideal world, should be directing their kids not to play raucaus games in the street to begin with. Since they're not providing that kind of guidance, you may or may not be able to count on them. Maybe the parents will think a rewards program is a good idea and will enforce whatever system you come up with, or, better yet, organize it themselves. Maybe they will think you're a meddling SOB who should mind your own business. It could go either way.
That's where punishment comes in. You can tell the kids that they have to move their game or you'll call their parents, but again, the parents are a wild card. You can tell the kids that if the ball is on your stoop, you'll take it from them and won't return it. You can threaten to call the police on trespassing charges or noise violation, which will probably scare the kids more than the parents, but, if the parents don't seem to want to resolve the issue with you, you could threaten that to them, too.
Whatever approach you take, be aware that they'll probably continue their game when you're not home, so you may not see the problem, but it probably won't disappear. Here's the "kids will be kids" part. It's summer, there are never enough parks to entertain all the kids who have a soccer ball and "street ball" has existed as long as there have been streets. So your last option is to plan to hold them accountable if the ball goes through the window, but otherwise lighten up and try to be glad on some cosmic level that they're outside playing instead of inside in front of a computer.