Don't mandate voting. If you mandate voting people will vote randomly. People will get elected on the basis of people just marking someone's name, usually at the top of the ballot. That's terrible. Also uneducated buffoons will be more likely to vote and that will get all the wrong people into power.
In fact we should seriously promote that if you aren't informed DON'T VOTE. Voting is good but only if you bother to inform yourself before you vote.