Protection can be anything from really easy to very complicated depending on your circumstances.
One of the easiest is just take some breaths, sprinkle yourself with a few grains of salt and envision a protective cloak around you of material that's shiny on the outside that will bounce back any negativity at the sender.
If you're not a great visualiser, a bit of tinfoil on your heart chakra (middle front of bra) shiny side facing outwards is fine, or wear a top with sparkly thread in it if you like them.
The whole point is to find something you can do for yourself that you feel comfortable with to make yourself reflective instead of absorbent when you are around those people or places.
I have a reflexologist friend who could not stop absorbing all her clients' ills, she tried all sorts and one day bought herself a doctor's white coat. For her, that works like a dream, it wouldn't work for me.
I'm a fan of flaming blue pentagrams and mirrors or shiny things to deflect, other people like salt or oils or smudge sticks or purifying baths or verses said three times or a load of other things. Experiment until you find something you're comfortable with. It doesn't have to be complicated to work.
If you go for the reflective methods, (hi viz jacket for the inner self) don't forget to take them off or end the process when you're out of the situation as sometimes people can be so protected and deflecting they forget to let the good things in too.