A must read from the Globe and Mail, Be a Smart Voter. (Via Volokh).
When you vote you are exercising the force of the government over your friends, family, neighbours, and countrymen. You have no moral imperative to vote, but if you do vote you have a moral imperative to those around you to be informed and to vote responsibly.
This is one of the reasons I oppose compulsory voting systems, like Australias. If someone is not voting because they are disinterested, uninformed, or unable to decide a voting preference, they are exercising their right to vote (or not, as the case may be) responsibly by recognizing this and refraining from forcing their disinterest and lack of knowledge on others. It is those who go to the polls because when they are uninformed or undecided who are acting irresponsible. They are the ones who are exercising the force of the state against their countrymen without either understanding the consequences of their actions or not heeding their understanding.
So be informed. Learn the party's platform and promises, then learn whether their platform will actually benefit your country or harm it. Learn the social sciences so you are capable of understanding the effects of various policies. The most important social science to learn in regards to government are the political sciences, statistics, and economics.
The political sciences are important so you know how our system works. A respected introduction to Canadian politics is How Canadians Govern Themselves, which is published by the Library of Parliament.
A less respected work I'd recommend is an American humour book, Parliament of Whores. This book illustrates, in a humourous manner, the reasons that government just sometimes doesn't seem to work as well as we'd like (and no, it's not because bureaucrats are lazy and politicians are evil).
For specific political topics, there are too many to give an intro. book for each, but wikipedia is always a good place to start. It will often have
Statistics is important so that you can understand what those numbers politicians, newsies, and that jerk on the internet love to constantly throw at you actually mean. The must-read classic on this is How to Lie with Statistics. It's a simple read, is not that long, and has all the basics you need to know so that you can protect yourself from being lied to by statistics.
Economics is probably the most important thing to know when you are studying the issues. At the route of almost all government issues are economic issues like taxation, spending, the redistribution of wealth, and economic control. Economics is also the area that (and many politicians) seem least knowledgeable about when it comes to voting. I would highly recommend Naked Economics. It is simple and easy to understand, but detailed. Definitely a must read. Learn economics.
So, if you are going to vote, be informed. If you aren't informed, be responsible and don't vote (or at least spoil your ballot, if duty compels you to vote anyway).