Besides showing off everything your robot can do, I'd suggest just being spirited, good sports, and sociable with the other teams.
At the KSC regional, we (180) were paired up with 186 for one of the early matches--we won, and both our teams ran into the pit, jumping around, hugging each other, and chanting for each other. We established a pretty good friendship then... and as most of you know, they later picked us. And the rest is history
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But seriously, if we hadn't made friends with them like we did, they probably wouldn't have picked us up later.