You want to beat the average on the AWA (the average is a 4). You specifically don't want to go for a 6 (perfect score) because you have to do the essays first, and the brain energy it takes to get a 6 will sap your strength for the multiple choice portion, which is what the schools really care about.

GMAC / ACT do not publish much info about the scoring mechanism for the exam; it's proprietary. We know that approximately 1/4 of the questions in a section are experimental and, therefore, not counted in our score. They do not publish how they score the individual questions, but each question is worth essentially the same amount as any other question, of any type, on the test.

We can tell anecdotally (from examining students' raw math and verbal scores and their combined scaled scores) that the test tends to weight verbal a little more heavily in the overall score than the math. But this information again is not published or officially confirmed by the test-makers.