* "Oh please dear boat crew, don't pair me with the guy that has the alert horn or the tank banger." Annoying yes, but you can always just ask that they don't use it on the dive...
* Same with snorkels. Some people dive with a snorkel. Some people (including myself) don't.
* Same if all of their gear is from the same manufacturer. My personal best red flag. Why is that a bad thing? Okay, I have kit from various manufacturers, but big deal if they have stuff from the same one.
* I lose all interest in my new insta-buddy when they want to do the BWRAF check. Why? I may not do a BWRAF, BAR, or GUE-EDGE (depending on who I'm diving with), but I always do some sort of buddy check. Even if it's just a quick, silent check of each other's kit. It's stupid not to do one in my opinion.
* Old gear. Awesome, I want that diver. I know plenty of divers with old kit I wouldn't do a 6m dive with in a local muddy puddle. Kit does not make the diver.
* If they are hyper on the deck they will be hyper underwater. Wrong! I'm quite a hyper person (I drink a lot of caffeine, sue me), but underwater I'm one of the most chilled out people I know. Being in the water relaxes me and shuts off the constant sh*t running through my brain. I can't sit still out of the water and need to constantly be moving and doing something.
* If they confess to being a new diver. Not usually a bad experience. I concur. I've been diving with some great new divers. I had a blast over the weekend doing a couple of dives with a new diver from my club, just bimbling about a local quarry.
* If in the first five minutes I get their dive resume, usually a bad experience. Not necessarily. In the off chance I'm diving with a random, I want to know what they've done.
* Cruise ship diver. "Danger, Will Robinson!!!!" It depends...
* Tattooed divers are good divers. Ummm....?
* Tip the crew hard early in the trip and you will get a better insta-buddy. I abhor tipping. I'm becoming more European by the second. I'm paying for a service, why should I have to tip in addition to it?
* Beware of dive operations who take this stuff too seriously. Usually means a nanny state. That's why I love diving in the UK. I book onto a boat with my mate. If for any reason he/she calls the dive at the surface, I can continue my dive solo if I so chose. No one cares. They are a shuttle to and from the dive site. You write your emergency contact info, tank size, gas, and planned bottom time on a sheet and off you go.
* There is no substitute for personal responsibility. THIS