Originally Posted by artbyjody
Go over it like you would buying a used car (or new for that matter). Get into every nook and cranny (you'll pick up things that the surveyor may not). Look for broken items, dark colored wood that indicates wood rot, check and make sure all the buttons, switches, etc work and if not labeled what they are used for etc, check all the bildge accesses, locate all the tanks and seahulls...
Take time to also chat with the owner if on board and ask questions - but more importantly ask them what they found to be weaknesses or annoyances with the boat - and what you should be aware of in terms of the boats quirks...
You'll be surprised how forth coming people are when asked directly.
Most of all - after clamoring around and soaking where things are - take a few moments to relax and consider if this is the boat you see yourself doing whatever style of sailing you intend...
This is all very good advice - but this is something you should have done long before the sea trial. IMHO, the sea trial is really just the icing on the cake. Way BEFORE you make an offer on the boat you should be crawling all over it looking to see what is wrong. Then, if it passes your test, you make the offer. Then you negotiate with the broker / owner. Then you arrange for the survey. Only after the survey has been done (at least most of it) should the sea trial occur (really, it's the last part of the survey).
If the surveyor finds serious problems with the boat, why would you waste your (and everyone else's) time on a sea trial?