One of the pet tips that comes back every year is tax loss selling of marketable securities. If you are in the market you likely do have some stocks that have gone down in value. The first question is do you want to sell them for investment or cash flow reasons. If not, don't unless there a substantial tax benefit. If you had a significant capital gain from 2009 to 2012 that you could offset by your unrealized capital loss you might want to consider it. December 24 is the last trading day on the TSX to do a 2012 transaction.
You can write-off capital losses only against capital gains. You can apply capital losses against capital gains in the current year, the prior three years, or carry them forward against future capital gains. If you have no capital gains in the current or prior three years, and are not planning to sell something with an unrealized capital gain in the near future there is no tax reason to crystalize a capital loss.
If you do sell an investment for the purpose of creating a tax loss you can buy it back later but you have to wait more than 30 days otherwise the tax loss will not be usable. Of course the market price could change in the interim. By the way there are rules to prevent you from creating a capital loss by a non-arms length transfer or a transfer to your RRSP or TSFA. The capital loss will also be negated if you or an affiliated person bought the same property within the 30 prior days. See superficial loss at the CRA website for full details.
Another favourite year end tax tip is top up your RRSP. If you are retired or working part time you need to think before you jump in with more RRSP contributions. What goes in must someday come out. When the money comes out it will be included in your taxable income at whatever marginal tax rates apply for that year. If the tax rate you will pay is as high as or higher than the rate applicable to your contribution, the benefit is questionable, iIt would depend on how long it will be before you have to take the money back into income and what rate of return you earn on your money while it is in your plan. The deadline for making a 2102 contribution is March 31, 2013. The amount you can deduct for 2012 is shown on your Notice of Assessment for 2011.
If you are in the process of retiring you may be able to transfer part of a retiring allowance into your RRSP. See the RRSP page on my website for details.
You may want to consider a spousal RRSP. You can make a contribution to your spouse's RRSP and deduct the contribution on your return if you have the contribution room available. Provided the money is not taken out for three years, any withdrawals will go into your spouse's income. If your spouse has little or no other income this can result in significant tax savings.
If you turned 71 in 2012 this is the last calendar year during which you can make contributions to your RRSP. The RRSP will mature on December 31, 2012 so you cannot make any contributions after that date. As well, you must convert the RRSP to a RRIF or use it buy an annuity; otherwise the RRSP will collapse and will all be included in your income. See my RRSP page for more details. If your spouse is younger you may be able to contribute to a spousal plan even if your plan has matured.