Making changes is up to you really. Since your excerpts are small and they seem to be for practice, I wouldn't bother that much. Improvements can be made in new excerpts anyway, aye? =P
I like the first and third one, and the only reason I'm not as hooked into the second one is because, well, I'm not sure where it's headed (besides derp hurr down a hallway). That being said, it's a nice line/hook.
I like the first one because I'm not sure which way it'll go. I always liked to read romance from the perspective of a boy, and this boy seems to be one who doesn't have the good self esteem. Should be intriguing. I really liked this line, too:
I liked the third one especially because it different. While contemplating love is fine and dandy, it's much more common then, let's say, a person who wants to fly. XP I liked how the speaker wasn't aware he/she was flying, and when he/she did, he/she fell. I get that feeling a lot. Er, not with flying, but with other things. I always hated that, when you're doing something, then you realize you're doing something, and all of a sudden you can't do it anymore ...
Either way, yeah. I can't really comment much, but they are interesting premises.