how should i...?

Well first off, make sure YOU tell her, and not your friend. Girls like taht better =).

What I would suggest would just be to tell he flat out how you feel, i mean the worst she can do is say i don't liek you back? and sure it may be awkward at first, but if she's a true friend, she'll eventually get over it.

Another possibility would be to write her a note/email/message or comment on myspace/facebook or something. That way, you won't have to do it in person, and it'll be alot easier.

Maybe try bringing it up in casual conversation, like joking around. Then depending on her reaction, either continue on with it, or just drop it.

But I DO RECCOMEND you tell her, beacuse trust me, you WILL end up regretting it if you don't.

Good luck, and I hope this helped =)