oh god...

You should always tell the person in person. unless they asked you out over IM or text or whatever. but..its usually alot better to tell them in person, just out of respect. remeber to build up their self esteem and tell them about how great they are and how you want to be their friend, but dont have romantic feelings for them. but its important to stress that you want them as a friend, to kindof dampen the feelings of rejection that may/will follow.