I back up and run into them again!
Depends on how close I get to them... but I usually smile and say HI and keep moving on
Just be courteuos smile and ask them how they are. Very little small talk then remember I have an appointment and am already 10 minuyes late.
Usually, I try not to make eye contact but if i do, i smile brightly and say a big hi, hug them and shake hands. I try to forget about unpleasant things and Its good to have manners.
I usually just smile and nod if they don't know I don't like them. If they KNOW I don't like them and I know they don't like me, then it's pretty much just ignore each other awkwardly.
I run into people I don't like nearly every day. they are called my family. i usually just try to remain civil, unless I am pushed.
I'm usually polite, but if it's someone I really, really don't like, I'll typically ignore him or her.