What should I do if I find a dog that's obviously lost? I don't know it, so how can I keep from being bitten?

Depends on the dog and how much danger the dog is in. If its in the neighborhood and looks friendly, I will try to catch it. If it looks mean I call animal control.

Last month I was at a bank (on a busy street) and a loose dog came up to me as I was getting in the car. (he was HUGE). I opened the rear door and he got inside. I drove him to the no kill animal shelter as I couldn't keep him at home and was told his owners found him there. (he was well groomed with a collar but no tags)

If the dog is mean or looks wild (no grooming, no collar, skittish, etc) call animal control. If the dog looks friendly you can try catching it and finding the owners.

if possible, try to get the dog into somewhere safe. finding a willing (NOTE- willing!) person with a fenced yard or kennel where you can lure the dog into is a good idea to keep it from getting hit by a car or something. the best way to do that is simply by placing something tasty inside, and then closing the gate after the dog has entered the area.

always call animal control, but don't approach the animal or try to grab it. throwing a good amount of biscuits or food on the ground can sometimes keep the animal there until animal control people get there.

I personally just use slip leads and haltis, but I don't care if I'm bitten to be honest.

I'd just call animal control if you're not sure of it. Otherwise, buy a slip lead (not a choke chain) and a halti (headcollar) and slip them over. Then put posters up. I'd suggest just calling control.

Call animal control. A concerned owner will be looking for it.