I was really hoping someone more knowledgeable would answer this as right now I am experimenting with different character setups myself.

If you go to create a new document and click on the presets button then click the Animations option on the left-side column you will see a simple character as the last scene to choose from. Select Character and click OK.  You'll see the character has some green null objects around it and the foot shaped objects should prevent foot slipping and keep them from passing through the floor.  In other words you should be able to create your own null objects and attach them to your character's skeleton to do what you need.

Although with that said my results have been less than stellar so far. So I'm still experimenting.

I hope this helps.