ok...
by "cancel", do you mean canceling out of a super? if so, this is not possible.
but, if we're talking about canceling the recovery time from one move to another, which creates a combo, i can help you.
a good example is with Vanessa. Try doing f + A alone, by itself, she should do two punches. that is a command attack. if you do C alone (close), it should do two punches.
these two attacks can be chained together, using the basic combo formula:
Standard Attack -> Command Attack -> Special/Super attack
in this case, we are doing Standard Attack -> Command attack. so, what you do, is C and then DIRECTLY after the second punch, press f + A and you will get two successive punches afterwards.
from these two punches, you can do a multitude of things, like a super or a special.
try this combo:
close C, f + A, hcf + C (tap C rapidly). you should get 10 hits, and in it, you should know that you have executed TWO cancels.
if you need more help, go here:
http://planetshogo.com/dash/faqs/koffaq.txt
it's a combo guide i wrote, and it explains the combo system in a much more thorough manner.