Something i didn't know until I was 22; sipping on coffee, or energy drinks through out the day hurts the enamel on your teeth and leaves like a yellowing on the gums. The stains don't go away but you can repair the enamel i think. Flossing is also really easy to do and you should get in the habit as soon as you can.

Also.. Cavities are bad, but once the dentist fills them in that doesn't mean you can get an unlimited amount of cavities and keep filling them in. Each time you're susceptible to getting another one. Right now one of my fillings is continuing to have pain even after x rays and more than one dentist checking it.. they don't really know why. Don't be like me. My teeth aren't even that bad and i always brushed them growing but but I /needed to floss/ and get under the gums to prevent cavities... Which i do now almost every single day.