Staying still should work. Main downside with that you will basically be "waiting" for the wasp to move on which isn't a very productive way of dealing with them.
Best thing is just to ignore them if possible. And when they get to close to your face for example, instead of swatting at them, gently pushing them away with your hand is usually more effective
I guess running away is an option. But it's very hard to enjoy a BBQ outside while constantly having to run.