I vote up questions that are good questions -- they're not covered in the FAQ, they haven't been asked before recently, and they show that the poster has attempted to understand the issue before posting.
I vote up answers that are technically correct (as far as I can tell), that contain more information or a different approach, or that point the original poster to additional information.
I vote down posts that are personal attacks or blanks (if no one else has set them to -1 yet).
I hit Worst Nodes daily... I'll bring mediocre stuff up to -1 or 0 if necessary (especially if it's a registered user -- no sense in driving people off).
Posts that are technically incorrect or need more explanation deserve encouragement, not --, so I usually send a message to the poster offering unsolicited advice.
I hate to have unwittingly re-hashed an old discussion, but some great posts resulted.
Voting guidelines appear to be highly individualistic, but could a collage of the responses perhaps be added as "suggestions" to the Voting and Experience System ? Would it be worth vroom's time ?
Update: zdog has graciously offered to write the "Voting Guide Faqlet" that mdillon and Russ recommend below, and I've encouraged him to run with the ball. I'll be unplugged for a couple days, and I expect zdog will do a better job with it anyway. :^)
to me, this appears to be an excellent candidate for a
faqlet in the Voting/Experience Information section of the
Perl Monks FAQ. it would be nice if someone collected
together the recurring suggestions among these numerous
threads about voting guidelines into a single
"Voting Guidelines" faqlet.