My dojo has a very brief one-page handout explaining the most common points of etiquette as practiced in our dojo - if your dojo has something similar, that's your best reference. If not, you might take a look at some other dojos' etiquette info (you can probably find quite a few on dojo websites, or I'd be happy to share ours if you'd like it). Bear in mind, though, that practices vary from dojo to dojo -- some dojos line up with seniors to the right, others to the left, and that's just one example. Etiquette and culture are definitely a "when in Rome" thing.
Ours has a handout as well, but I would advise just paying very close attention to what everyone else does. My Sensei is very very relaxed about a lot of points of etiquette, but we get a bit more traditional when we do camps, or train at other schools in the organization.
My biggest rule of thumb is, always bow, and never turn your back on the instructor. If you are going from seiza to cross legged, seated to standing, about to start waza with another student, just always make sure to bow. Also, if you have any physical issues with things, let your Sensei know before class. I've currently got a fairly bad knee, so I can't do a sayu nage on my right side, nor can I do things like shikko. Sensei knows my issues, and isn't worried when I bow out of certain things to sit on the edge of the mat. It is important for the instructor to know your physical limitations before class so s/he doesn't have to interrupt class because they are worried about something they should have already known about.