Minnows should not worry too much about voting. They can do it to show support, but neither they nor the recipient will make much. Just vote up the posts you think are good and don't worry about curation rewards. Make good posts/comments and you stand to earn from those.
Of course votes also affect the order of comments in the default view (does anyone ever change that?). If a crap comment is top then even a small vote on another comment can move it up.
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.
Totally with the axeman on this :-)