1. Don't vote if you thinking voting means you get your way. It doesn't. Voting is a process that includes all sorts of other people, some who agree with you totally, some who agree with you partially, some who disagree with you, and some who picked the prettiest names. If your expectation is that by voting the candidate or issue of your choice will succed, you are in for a lot of disappointment. If you are not prepared for the fact that the majority of (voting) people may feel differently than you today - don't vote.
2. Don't vote if your under-age or otherwise not eligible.
3. Don't vote if you hate doing research. Alright, I certainly can't prevent you from picking the prettiest names, but if that's all you've got, then why spend the time getting to the polling place at all. If you just like stickers, call me, I'll send you some. Look, you don't have to know enough to write a dissertation or anything, but get an idea. Whether your focus is a key issue or two, or you have a running checklist of pros and cons is up to you, but have a clue. Otherwise, don't.
4. Don't vote if you hate being wrong. Sometimes you will select people who seem great and they will turn out to make different decisions than you thought they would, or they will turn out to be a crack smoking, spouse cheating, bribe taking idiot. Just like in real life, sometimes your first, second and twentieth impressions of people will be wrong.
5. Don't vote if you don't care. Seriously if you don't care about roads, rights, education, the environment, taxes or war then there's no reason I can think of that you would care who's elected. So, don't rush.