Buy a good crosscut shredder that can handle CD/DVDs and credit cards. Always shred:

1) Junk mail that have applications in them such as credit card offers (I shred the whole thing).
2) The address of all your mail that you recycle or throw away. (there have been cases of people digging through trash at the landfill to get addresses and names).
3) All expired credit cards or those that you close.
4) Copies of important documents you don’t need any more.
5) Any paperwork with important numbers and/or your address on them.

This closes one area where identity theft occurs. If its properly cross cut shredded, there is little chance a thief can get your personal information.

It only takes a little discipline to get into the habit. I place my shredder right next to the area I handle paperwork and bills. It is easy to make a shred pile, then lean over and feed the machine.