What is the proper technique for using thinning shears?

Answer 1

Take a thin slice of hair (going up and down on your head), hold it between your fingers without putting any tension on it, where the hair naturally bends, do not thin any closer to the scalp than that. Do this all the way around.

However, if you take too much out you will look scraggly and your hair will tangle. You are better off going to a salon.. but either way, do not thin long (shoulder length or longer) more than every 4 months or you will end up with poofy on top and thin on bottom.