I see by one of your earlier posts that you're around 15-16 years old, right? Not that that makes a whole lot of difference, but it probably means you can't play in bars.

I'd recommend coffeehouses. I don't know where you live, and I don't know if the trend has reached everywhere yet, but in the urban areas I know, coffeehouses are springing up everywhere. Stay away from the big chains like Starbucks or Caribou, and instead look at the independent ones. They're usually pretty low-budget affairs. They usually don't pay at all, but they might give you free coffee, maybe even a free pound of coffee beans to take home, and maybe some other freebies for musicians, and they should let you put out a tip jar. And they'll usually welcome you and your friends, especially if your friends come ready to spend a little money.

Try to find out if any coffeehouses in your area already regularly have live music. If they already have musicians booked for Friday and Saturday night, and they're reluctant to let beginners play on those nights, then ask if you can play on, say Thursday or Sunday. Or maybe Saturday, but earlier in the evening, before the regular musicians come in. Or maybe Sunday afternoon. If that fails, try a coffeehouse that has never had live music before.

Don't worry about the fact that they may have had only rock 'n' roll until now. A lot of people are getting interested in folk music recently, since the film "O Brother, Where Art Thou?" And even MTV has had "Unplugged" (is it still around?) so acoustic music should be nothing strange.

Don't be too eager to make money. I mean, don't think you're a failure if you don't start making money right away. Your first sign of success will be when somebody applauds, or maybe drops a quarter in a tip jar. Your second might be when the coffeehouse manager agrees to let you come back. After a while, you may notice that a few audience members who have heard you before, come back deliberately to hear you again. You have to learn to appreciate the little signs that people appreciate you.