What are some ways to prevent cavities, gingivitis and periodontal disease besides brushing?

Prevention: Chewing sugar free gum is very efective(esp. Gum with xylitol)reduction of sugar, softdrinks etc also helps.

Floss: Flossing and use of mouth rinse like listerine.

Nutrition: Along with brushing, flossing, and rinsing, it is important to have great nutrition. Please cut down on sugary snacks, and eat lots of fruits, and vegetables!

Flossing and...: It is vital to floss, to do it well and regularly. Additionally, keep up with your recommended hygienist appointment intervals, and try to stay in overall good systemic health. Do not be reticent about discussing your personal risk factors and asking about re-reviewing oral hygiene skills with your dentist. Prevention is just as important (if not more) than rehabilitation.

No magic bullet: Preventing cavities can be accomplished by reducing sugar intake, especially sticky sugars like raisins, dried fruit, caramels, etc. Gingivitis and periodontal disease can be reduced by brushing, flossing and using oral rinses. there is no magic bullet: you have to work at it to stop its progression.