If you don't want to use lice shampoo, I believe putting a few drops of tea tree oil in your shampoo is a good way to get rid of them.
I unfortunately got lice as a teenager from my cousin and they didn't even tell my parents right away that their daughter had it.
Anyways, long story short. I used tea tree oil in my shampoo and it got rid of the lice. Doing it as a preventative measure shouldn't hurt.