1. Get rid of your land line.
2. Register your cell phone on the do not call registry.
3. Don't answer any numbers you don't recognize.
Two quick stories:
My parents have hardwood floors, and have for years. My mom got a call one day to have her carpets cleaned. She said she had wood floors and the caller said, "Lady, don't lie" then hung up on her!
When I was still living at home, I answered the phone one day and it was a telmarketer who wanted to clean our chimney. I told them that we had a wood stove, and that we just dropped the cat down it a few times when it seemed like it needed to be cleaned. They hung up on me.