One thing minnows should not do is self-vote. It can put people off supporting you.
Comments or posts? I know we have slightly different viewpoints on this topic, though lately I haven't been voting up my own posts either.
I still maintain it's fine to up-vote your own post though.
They shouldn't upvote their own comments, but I don't think anyone should. Let others decide which comments rise to the top. If they self-vote their own posts it doesn't make them much anyway.