The easiest way to make something like a t shirt is to model it (this can be done by duplicating the faces around the body where the tshirt would lie and scale them out a little) and then select the geometry and go to 'nCloth' > 'create nCloth'.

You would then make the body interact with the shirt by going to 'nCloth' > 'create passive', or similar to these tabs (I don't have Maya open so can't be more specific).

That is the basic way to make something like that, you would then need to start tweaking with the attributes of the cloth for desired effects, etc, but thats the basic flow as far as I can remember.

Chris