Prepping your board before drop-off
Before you go
Rinse the board and let it dry -- sand and wax on and around the damage make it harder to see what's actually going on. Take a few photos of the damage in good light before you clean it up, in case you want to show a shop ahead of time or compare afterward.
If you know how it happened (reef, rail-to-rail collision, fin strike, left in a hot car), mention it. The cause often tells a repairer as much as the damage itself, especially for cracks that aren't visible yet at the surface.
What not to do
Skip the tape, silicone, or superglue as a stopgap fix -- they don't stop water intrusion and can make the surface harder to prep for a proper repair. And don't leave a damaged board in direct sun or a hot car in the meantime; heat can worsen delamination on top of whatever the original damage already did.