1. Bring every part you can to the field just in case (ATL). Murphy's Law dictates that the one gear you don't have a replacement for is the one that will break.

2. Forget to tighten loose bolts. Realize later that part of your frame is only staying together because being hit so often (Ramp Riot, it was a pretty contact-heavy year with the King of the Hill bit) bent two pieces of the 80/20 together...and that there are no tightened bolts on that corner of the robot.

2b. Fix that. Something worse will go wrong (see 1).

3. Wire a battery backwards. (Thankfully we caught this when we were checking our batteries in the shop before we tried to use it).