Practice talking to male strangers, regardless of whether or not you like them. Conversation is a skill, and a familiarity with the process of breaking the ice, moving from one topic to the next and discovering more about the people around you will help to bolster your confidence when the time comes to talk to your crush.
Pump up your ego. Write down a list of things you like about yourself, keeping in mind not just your body, but also your brain, your values, your talents and the kinds of relationships you keep. Dress in clothes that make you feel attractive. Exercise or engage in your favorite activities so you'll feel confident, capable and positive about your self-worth.
Research your guy's habits, likes and dislikes. Talk to friends and friends of friends, and casually ask them what they know. If you discover that he loves to hang out at the city botanical gardens, make it a point of bumping into him there. If he's a member of the debate team, consider signing up. If you discover that he's into foreign film, keep that in mind as something to bring up if and when your conversation lags.
Find any excuse to talk to him. Ask him if he's the guy who sits next to you in calculus. Ask him for directions. Ask him for the time. Ask him for a restaurant recommendation. Ask him if he knows so-and-so. Compliment his coat, his shoes, his backpack, and ask him where he bought those items. The best way to start a conversation is to get him talking, even if it's about something benign. That will give you time to ease into the exchange and figure out what to say next.
Remind yourself that you have the right to talk to him. If you put your crush on a pedestal, it's easy to behave like you're in the presence of a movie star -- giddy, nervous, frightened. Remember that no matter what happens, you are his equal.
Calm yourself if you start to panic. Maintain eye contact. Breathe. Remember, if all else fails, let him drive the conversation. Continue to ask open-ended questions to get him talking. Be a good listener; you don't have to perform.
Make a joke about yourself, someone you know or something around you. Try not to sound negative or sarcastic, but easy going, someone who doesn't take herself (or anyone else) too seriously. People feel most at ease when they don't have to worry about being judged. Remember, he might not know what kind of person you are. Demonstrate that he has no reason to be wary of you.
Slow down. The only thing you need to do when talking to your crush for the first time is, well, talk. That is a huge first step. Keep an open mind about where your relationship will go next. There doesn't need to be any pressure to hook up or to let him know just how much you like him. After getting to know him, you might decide he's not so great. Give both him and you time to figure out what you want.
Assert yourself with subtlety. If you do want him to know you're interested, it's best not to lay it on too thick. Move closer to him. Briefly touch his shoulder or arm. Laugh at his jokes. Invite him to meet up with you at a place you know he already hangs out. You don't need to play hard to get, but you can walk a line between being obvious and seeming totally aloof.
Prepare yourself for disappointment. Again, he might not be the guy you thought he'd be. Maybe he's boring. Maybe he's a jerk. Maybe he's uninterested in you. All of that is just fine; these kinds of experiences allow you to "get over" him faster. What's most important is that you know where you're headed next, if he's worth your time or if it's time to focus on someone (or something) else.