I'm assuming that you are not hunting as that would require behaving in different ways. I'm also not discussing camping/camp which is covered very well by this question: What precautions should I take to protect myself and my camp from bears?
In black bear territory, but prior to seeing a bear:
- Make noise. The bear will generally move away from you. Just talking and not being stealthy is usually enough. I've seen information for and against the effectiveness of bear bells. They can't hurt but they may not provide anymore protection than just being generally loud.
- Watch your back. Bears will tail people. I'm aware of multiple cases of people looking behind them only realizing there's a black bear that is following.
- Don't drop food and don't wipe your hands on your clothes. Do what you can to avoid smelling like a meal.
- Watch your surroundings. Bears are more likely to be encountered near streams. Also look for trees they have clawed as that means you're in their territory.
- If you have a dog in black bear country keep it on a leash. There have been cases of dogs aggravating bears then running for their owner/protector... bringing the bear with them. Or my least favorite hiking encounter when a couple said as they passed "Bears ahead, our dog treed a cub..."
Face the fact that you are not a guest. It is entirely possible that, if hungry enough, even a black bear will decide you are food. If that is the case then no amount of being polite will help you. The vast majority of the time this will not be the case, but that will be of no comfort if you are attacked by a hungry bear.
If you do see a black bear:
Most times, if you run into a black bear it will just take off. There is really no "encounter."
Caveat what follows with the fact that I am not a bear expert (as in a biologist who studies and works with bears for living), and this is second hand advice:
If you actually encounter a bear checking you out, it is hard to say the correct behavior because that will depend on why the bear is checking you out. Unless you are a bear expert then it's unlikely that you will be able to tell the difference between curiosity, hunger, or other bear reactions/moods. Unfortunately they require different behavior on your part to avoid any unpleasantness.
For a 'go to' default: Back away slowly. If it persists and follows you then go with the make noise and look bigger approach (bang hiking sticks, yell, etc). If it charges, stand your ground as it can outrun you anyways and you don't want to look like prey. If it attacks then fight and pray. You'll probably lose, but once it attacks you are out of options.