This is the half step counting chart which I let my students use in the beginning (along with a piano sheet) so that they can physically touch and see how to build intervals. There is infinite practice along with this handout: give the first note of an interval (i.e. a perfect fourth up from C) and have them build it; give them both notes (i.e. C - Eb) and have them name the interval; practice enharmonics; etc.
If you choose, you could eventually have students wean away from this list by memorizing it in its entirety; I personally never did this, though I did make them keep up with their handout.