Boating is fun but it can be dangerous. "Safety First" is a good motto. I'll have all the required safety gear and will go over the basics before we go out.
Bring a sandwich/finger food/snacks/stuff to drink if you'd like. There are a few delis on Grove Street when you get off the PATH train in case you want to grab on the way and there's a good wine/liquor shop on Grove and Montgomery.
Generally you should dress in layers and in comfortable clothes you can move in. Bring a bathing suit if you'd like, we might go swimming if conditions are good. Avoid long/flowing dresses or things that can snag on rigging. You may want to bring a hat and sunglasses too.
At night it often gets chilly so bring an outer layer in case you get cold. I have stuff too just in case.
If you have boat shoes, bring them. If not, sneakers/flats/sandals that have a rubber sole are fine. Avoid: leather soles, flimsy flip/flops (more robust flip/flops would work). Basically you want something that grips well and offers your feet some protection. Barefoot is typically cool when we're sailing, but during docking you'll need good shoes.
I have LOTS of sunscreen, but bring your own if you'd like.
It's important to drink enough water especially when we're out during the day under the sun. You'll be more prone to motion sickness if you're dehydrated.
There is a marine toilet on the boat, so no worries about drinking lots of water... :)
There's plenty of room to stow gear onboard, so feel free to bring extra clothes, camera, cliff bars, etc. Don't over do it because hauling a lot of crap sucks and you probably won't need that much.