My opinion is this: wait for them to ask you. If you bring it up yourself, they may not be ready for it. When they ask you, then they are ready for the answer. If someone asks you, "Are you gay?" just say, "Yes" and leave it at that. If they ask you another question, answer that truthfully. If someone asks you, "So, do you have a girlfriend?" just say, "No. I'm gay." and leave it at that. If someone offers to hook you up with a girl, just say, "No, thanks, I'm gay. But thanks anyway." If they want to know more, they will ask you more, and you can continue to answer truthfully. If you bring up the issue yourself, without them having asked you, then you run the risk of telling someone who is not ready to hear it, or won't accept it, or doesn't want to know, or doesn't care. When they ask you, however, they are ready for the truth and you know you can tell the truth. This way of dealing with it takes a great deal of pressure off you. There is no pressure on you to tell anyone, unless they specifically ask you.
this is some really good advise... I have never though of this before. but i doubt any of my friends will ask