Usually when playing any instrument, if I'm tapping my foot:

If the music is 4/4 ("common time", 4 beats per measure) I'll tap on the 1st and 3rd beat in each measure. In other words, ONE two THREE four.

If Im playing a waltz or 3/4 tune (3 beats per measure), I'll tap my foot only on the ONE beat in each measure... ONE two three. I hope that helps.

I'd be glad for any advice experienced players can share on keeping time with a foot tap or metronome.  Where does the tap/click fall in relation to the sheet or played music?  Especially with a dotted note, e.g a dotted quarter note in a measure of 3/4 time.  

Thanks!