How should athletes approach sponsors at trade shows like SEMA or PRI?

Trade shows aren't the best time for detailed sponsorship discussions. Instead, use them to introduce yourself, have a brief conversation about what you're doing, and grab a business card. If you hand over a proposal, they'll eventually look at it, but you'll get faster attention if you follow up with an email afterward. The personal introduction opens the door, but the formal proposal should come separately via email.