If your in the track meet don't worry, but I run track and if your going to see him just be yourself and wear what you think looks best, that's what my girlfriend did the first track meet of mine she came to and now we are deep into our relationship.
Well look cute but not too sexy. Wear hair up so it reveals you physic, like shoulders and ears and neck. You want to look attractive but not like you want too much attention. Something sexy but classy and respectable. Good?
If you are going to a track meet you don't have that many options. Simple, clean and activity appropriate is key. If you want to get his attention, I think you need to do that with your personality/behavior. Just be friendly. You already know you two have something in common and will be spending time together, so it shouldn't be that hard.
Just smile and try to get a chance to talk to him (or give him a chance to talk to you) it doesn't matter so much about what but if you are really interested and want him to think he has a chance (if he is interested), you actually need to interact a little so that you both feel more comfortable. Good luck!