If you're not too shy to tell her how you feel, you should do it. Most people can't do something like that. I would probably like it if some guy came up to me and told me that he liked me (as long as he wasn't really gross or something). It would make things easier on you because then she would know that you liked her and not have to guess.

This happened to me one:
A guy who I had liked for a few months was picking on me and being a little flirty and something got brought up (don't remember what). He said "it's because you want me, isn't it?" and it made it easier for me to not be shy and admit it since he already said it.
I don't know if anyone else would like that, but since I'm really shy it helped me.