The first thing I've learned about riding in busy urban traffic was the eye contact with drivers. Eye contact won't prevent them from opening the door in your face (all the while looking at you in the side mirrror), but it will alert you to that possibility. Eye contact will tell you which possible actions a driver (or pedestrian, child, etc.) can take, so you'll be prepared for the worst.

Which all boils down to matching your speed to your current agility, concentration and awareness, coupled with road and traffic conditions. This matching is done automatically by the brain in background already. Just follow your safety instincts and you should be mostly OK.

BTW there are books for efficient and safe riding techniques. I regard them as prerequisite for cycling.