In ASL, most of the grammar in an discourse resides almost exclusively on the face on the upper body. When I say "body movement," I mean torso and shoulder movement, not the general "movement of the body or any part thereof."

Tense, for example, is often spatially arranged so that backward movements and anything behind one's vertical bisection can be past tense. The space immediately in front of the signer can be present, and forward movements or the space farther out from a signer's typical signing space can be future tense. (notice "can be;" if I'm giving directions or have other spatially-oriented pronouns occupying spaces within my sign space, you wouldn't think I was messing with tense).

Another example can be found in various sentence types. Rhetorical questions are created and identified with raised eyebrows and a forward head tilt. WH-word questions (who, what, when...) have squinting brows with a forward head tilt, forward body tilt, or shoulder raise. Yes-no questions have brows raised, widened eyes, a body lean, and a very pronounced head tilt. These kinds of combinations can be found in directives, conditionals, negations, assertions, relative clauses, etc.

Also - what are classifiers in this context?

Ahh, what are classifiers? I'll post that separately.

Is there somewhere I should look online so that you don't have to single-handedly educate me on the basics and nuances of ASL?

A good beginning forum would be DeafWorldWeb's Resource library at http://dww.deafworldweb.org/pub/

Brandon