Stand very still, relax, and breath slowly. Put your hand over your nose and mouth and close your eyes to prevent them from entering your body or stinging your eyes. By breathing slowly you will have less carbon dioxide in your breath. Bees are attracted to the carbon dioxide. By standing still you are also not seen as an aggressor, if you run, then you are being aggressive. Bees will defend against an aggressor by stinging them.
Run - whilst some African species of killer bees are able to follow for quite some time realistically you just run to someplace sealed, ala a phone box, house, shop, or jump in a river, wrap yourself in a blanket, etc.
There's plenty of options, as someone who has had the misfortune to be 'chased' by bees I can tell you it's not particularly hard to outrun them, I just ran into the house and closed the door. Simple.
Pray it never happens ! I hate insects and cant run!
Swarming bees are usually just looking for a new home. If you're just talking bee's, they don't generally sting while swarming. (So says my brother, the bee-keeper)
Don't run, they'll chase you (killer bees can follow you over a mile). If they are just around you, relax and enjoy their company. Bees can sense (from your natural chemicals) if you're scared of them. If they begin crawling on you, get down on the ground and roll away, like you would if you were on fire. They don't want to be crushed. If you have a friend near by, have this person shower you with the water hose. Bees don't like to get their wings wet.
I was ones surrounded by bees it is natural to run like hell, but they still wrestled me down and had their way with me.
Run! It's not like the T-Rex where they won't see you if you don't move...;)