As some research says oily skin is hereditary, you can't just avoid them. all you can do is regular management. Just start with a basic. Don't over use the cleansers that tend to dry your skin. use noncomedogenic sunscreen and moisturizers products as they are oil-free and they won't clog pores. If you have acne its better to talk to your dermatologist about the drug treatments like Benzoyl Peroxide and retinoids
Here are few discussions that you might find useful:
http://www.dermatalk.com/showthread.php?t=66
http://www.dermatalk.com/showthread.php?t=1230
http://www.dermatalk.com/showthread.php?t=563
http://www.dermatalk.com/showthread.php?t=1270