Besides protecting yourself from the sun,the best way to avoid squamous cell carcinoma is to examine your body for any unusual growth or patchy areas and have a dermatologist look at them right away. Also, go to your dermatologist for a complete exam once a year.
I have had one episode of squamous cell carcinoma on my neck. It was cut out completely and the area was biopsied twice just to make sure it hadn't spread.
I was surprised to learn from this article that squamous cell carcinoma can settled into our tongue or other soft tissue.