Resting bitch face. While in most situations this expression/term is known as a negative trait, when you are trying to avoid people it can be used greatly in your favor. If you naturally have resting bitch face great use that. If not try to make a resting bitch face. Practice in front of the mirror or something and practice looking really stand offish and mean.  This has a fifty percent fail rate so it's not the best way to avoid people but if you keeping practicing you could become better at doing a resting bitch face and in the long run avoid more people.