I've spent a bit of my life as a commercial crabber. As others have said, the round pots work best. Dungeness crab aren't overly intelligent, at all, but they do become frustrated if they can't get in the pot and will leave. If a crab comes to the edge of a square pot too many times without figureing out how to get in, it will leave. Round pots don't frustrate them as much and they'll keep circling until they figure out how to get in. I've seen some underwater footage backing this up.
People in Puget Sound LOVE to steal crab pots. I've had several stolen. Don't leave yours unattended in Puget Sound, especially in the south sound.
Use a flag on a pole to mark your buoys. It makes it easier to find when the wind kicks up.
As far as bait goes, salmon eggs outfish any other bait. Period. Most people don't want to spend the money though. After that, try anything that comes from the ocean. Herring, anchovy, salmon, fish carcasses. I'm not sure why some people say to use the stinkiest bait, it's simply not true. Sure, stinky rotten bait catches crab, but crab only eat stinky rotten stuff if there is nothing else left to eat. I've also had good luck with chicken, for some reason I have not had good luck with turkey.
If you are catching undersized or females, move. The biggest strongest crab are the males. They take over the feeding grounds. When the good food is gone, they leave too and the smaller males and females move it to eat what's left.
If you are targeting dungeness and are catching rock crab, move. Rocks are a hell of a lot stronger and meaner than dungees and have no trouble tearing the limbs off a dungee. Not to mention, they usually inhabit a different range. That being said, try eating rock crab, they're actually better tasting, just a lot harder to eat and deal with.
with all that said, I'd just go buy a cheap "Danielson" pot and some chicken legs and go at it. You can get a whole kit for around $50 or so. Or if you're concerned with space, try the rings. They're a lot of fun, but you have to check them more frequently, plus, they outfish most other types of gear.
I have a game warden friend who says the rules in Washington are written in such a way that essentially every boat they stop is a violation. He said it's almost impossilbe to crab legally. For example, every crabber has to have THEIR name on the pots they pull. Only two pices of gear per person. As most of us know, when it's time to pull gear, you just pull whatever pot your group has set out, not neccessarily the one with your name on it. Also, make sure you know how to identify a male from a female, and how to identify a soft shell condition. Also make sure you record your crabs on your punch card as soon as you catch them, not when the day is over.