The thought of putting yourself in a vulnerable position is quite frightening, but that's exactly what you have to do if you want to tell someone you like him. A few steps will help to make the experience a little easier on your fragile heart.
Decide what you want to say, how you want to say it and when and where you want to say it. Preparing a small speech beforehand will ease some of the nervousness. It will also keep you from stuttering or mumbling, and possibly from looking awkward in front of your crush. Choose an opportune moment and place for your confession, such as when the two of you are alone together in a private location.
Realise there is always the possibility of rejection. Make sure that you are emotionally ready to take this important step. If your crush doesn't return the sentiment, you might find yourself extremely hurt or disappointed. Before you actually tell him how you feel, give yourself plenty of time to reflect on your decision.
Prepare for the possible reactions. She may or may not feel the same way as you. Hopefully, your crush will respond in kind. However, anticipating a possible rejection will help to lessen feelings of disappointment. In contrast, getting your hopes up will make a rejection that much more painful.
Tell him how you feel. You can either say it directly, write him a note or ask him out on a date. This is the hardest step, but you'll be relieved once it's over. Luckily, there is more than one way of divulging your feelings for another person. You can write him a cute little note, or ask a mutual friend to break the news. You can also ask him out on a traditional date--say, for dinner and a movie--and then tell him that you would like to date exclusively.
Accept her response in a dignified manner. No matter what she says, accept it gracefully and thank her for being honest. If she tells you that she is not interested, don't dwell on it. Just move on.
Being prepared is the key. Move through the steps slowly, even taking days between each step.
Rejection is never fun, but try and be thankful that possibly you missed a bullet.