I just got my iPad, I'm in love with it and the battery life is amazing. I know that some tablets or phones have weird batteries where if you over charge it the battery will slowly decrease over time. At what point do you guys normally charge your iPad? Like 30, 20%? And can you over charge it?

Make a search in the forum - lots of answers to that one.
Bottom line:
Charge as much as you want. As long as you want.
Do not fear.

Most sites recommend discharging to slightly below 20% at least once a month and re-charging fully. Modern electronics allow you to leave it on charge, most of the time, without any problems, unlike older devices that would overcharge the batteries and cause problems.