Orientation of the body (or parts of it) is an excellent way to see where one's interests lie or what he wishes to avoid.
Legs are a good starting point because they are honest, if we want to go somewhere we'll usually point there - with our feet.
Attention and rapport (or lack of them) are easily spotted by signals such as:
I. Head movements - nodding and tilting are obviously good signs! (But be sure that they're not rather a symptom of impatience with a fast nodding).
II. Resting the chin in the hand is also an attention signal, but it's very passive and usually means that whoever's listening - isn't very taken by the words.
III. Leaning in or out - a very honest signal on the level of involvement.