Foot placement in relation to the body, yes very important, being on the board consistently? well, some people think its not important in training. I happen to think otherwise. I think hitting the board consistently becomes a habit, eventually you want to be able to feel if you are going to be on the board after your first couple of strides. Personally i make an effort to be perfect on the board from all short jumps (8st, 10st,12st etc) and i rarely foul during meets, so i feel there is some correlation there. Also, being on the board will help you measure your jumps during practice.
Completely agree, get em on the board at practice. There is a definite correlation between fouls during practice and fouls during meets.