One-on-one, start with the easiest facts, 2 x 4, 2 x 6, etc and whatever ones are not known when asked, either orally or by writing them, make a note. When you have 3 or 4 not known facts, make flashcards for those, plus a few already known facts mixed in. Drill on those, then assign them for at home practice. Repeat the next time.
Use the web site for drill when time is not available for one-on-one drill. http://www.geocities.com/multiplicationfacts