1. Pick a contractor who has been in business for a number of years, because it isn't sheer luck alone that has kept him in business.
2. Pick a colour that is in the same colour scheme of your exterior.
3. Be sure to understand investing in a new roof. If you are looking for it to last a number of years, be cautious of saving a few pennies up front. It may cost you more in the end.
4. Warranties are only valid if installed correctly, and not all contractors are certified.
5. There are different products for different applications. Make sure you are getting what you need.
6. Consider a realistic length of time you will be living in the house and pick an appropriate shingle warranty.