The anarchists say that if voting changed anything, it would be illegal. That's not entirely wrong. Nor is Heinlein's Lazarus Long:
If you are part of a society that votes, then do so. There may be no candidates and no measures you want to vote for...but there are certain to be ones you want to vote against. By this rule you will rarely go wrong.
If this is too blind for your taste, consult some well-meaning fool (there is always one around) and ask his advice. Then vote the other way. This enables you to be a good citizen (if such is your wish) without spending the enormous amount of time on it that truly intelligent exercise of franchise requires.
Since you're reading this, you're already engaged in the second strategy. But I'm not planning to give you advice on how to vote. You can still, if you choose, do the opposite of what I suggest; but it won't work.
I suggest that everyone who's eligible should vote, every chance you get, even if there are “no candidates and no measures you want to vote for”.
Of course, as it begins to make a difference, the idea of outlawing it will come up. In fact, the Bush administration is said to have planned for the possibility of a terrorist attack forcing the postponement of the November Presidential election. Which, post hoc ergo propter hoc, means that voting is beginning to make a difference.
But seriously, folks, this world is pretty deep in the proverbial doo-doo. My claim is, we need to do something; we've tried doing nothing, but that didn't seem to help. Now might be a time for action.
And if we're going to do something, then either we all do whatever strikes our respective fancies, or we somehow collectively decide on what to do (or some mixture of the two). But in any case, someone has to decide.
This deciding stuff is not really rocket science. It's tricky, but that's because we all want different things, and we're not always honest about which ones they are, or what we're willing to give up to get them. There's no special body of knowledge required. Some people are better than others at presenting their points of view, true, but that's a skill that can be improved.
But there's no specialized body of knowledge or set of skills that guarantees success, or even makes it much more likely. Which, logically, means that no set of experts can reliably make the best choice; thus, leaving the decisions to the experts is no more likely to work than any other system.
In fact, if there's any tautology in my argument, it's that whoever makes the decisions is nearly certain to act at least partly in their own private interest. If they're feeling civic-minded, they'll find a way to identify their interests with those of the community, or make the community's fit theirs. But it's a rare decision-maker who can overrule personal interests for the public benefit. Certainly you can't base a political system on such people.
Plus, whether the decision-maker is a king or an aristocracy or a legislature or a corporate lobbying group, the private interest of the decision-maker is unlikely to correspond with that of non-decision-makers. In theory you could generate a database of all relevant factors for all citizens and choose a cross-section, but I don't want the government to know that much about me. And even then, choosing certain people to make decisions would automatically make them non-representative, because they'd have influence over the decisions.
Therefore, there is no subset of the population that is likely to make better decisions than the population as a whole. Thus, democracy.
(With apologies to Bertrand Russell and Noam Chomsky, from whom most of the above was cribbed.)