Preparation
Preparation is a vital step in achieving good results.

• I have found that with anything you do it is best to read and follow the directions of a manufacturer when using their product.
  
• What I have found as a good way to do this is to have more than
  enough of the chemicals that you need for any prep work before you start
  a job. (Acetone or wax & grease remover for example).
  
• Before doing any sanding clean the area to be sanded thoroughly with
  a suitable cleaner (Acetone or wax & grease remover for example). 
  What this will do is when you are sanding you will not be rubbing grease
  and dirt into your new surfaces.