how do you know if your timing is off? what happens when your timing is off? can the timing be off by a tooth and the car still drives smooth?

Sometimes, might have a intermittent miss, run rich or lean, depends on which way it is off. Best bet is to change when recommended to avoid engine damage if it breaks.

the car wont run very good

If your timing belt has skipped a tooth or off by about 6 degrees you would have no doubt in your mind that something was not correct.

Did you just have the belt done?
Hondas have the easiest belt to change if nothing moves while doing the replacement.