Robert Heinlein has to be one of the most quotable people since Shakespeare.

Here is what he said about Voting:

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.