Here's how to find fun: the easiest way is to have friends in the city you're going to visit. If you don't have any there, that shouldn't stop you from going. Someone else's friends will do just as well. This gives you a place to sleep, and humans need sleep. Otherwise, you could camp out, stay at a youth hostel, sleep in your car, etc. It's a good idea to arrive in a city with a place to stay or a full day to look for one; otherwise camp out in the countryside and get there early the next day.
Look for fun the same way you would in your home town. Check out the local alternative press; visit record stores, where there'll doubtless be flyers for shows and hep employees. Don't be afraid to embarass yourself in front of total strangers-- you'll never have to deal with them on a daily basis.
If you want to find specifically gay places, it's a good idea to own a copy of Gay Yellow Pages, since you can't always find the local gay paper to tell you where to go. You can buy a copy at your local gay bookstore or any other that's left-wing enuf. While the book is by no means complete--just check out the listing for your town to prove this--it's a good starting place. Check it in advance--you might want to plan your trip so you're in town on a one night a rockin' breeder bar "goes gay." Otherwise, you could just ask a waiter or hair stylist.