Entering Canada
When you cross the Canadian border at any port of entry, you have to declare cash or cash-equivalent instruments that you are carrying that are worth $10,000 or more.
When a bank transfers money on your behalf (e.g., by electronic transfer of funds), the bank declares the transfer on your behalf.
You do not have to pay tax on transfers of money into Canada (whether you bring the money in yourself or get a bank to transfer it for you). You only have to declare it. This rule has something to do with keeping tabs on money transfers so as to catch money launderers.
 Selling foreign assets
Once you land in Canada and are a tax resident of Canada, you do not have to pay tax on foreign capital assets that you own.
However, if you earn interest, dividends, rental income, etc., from your foreign capital assets, you do have to pay Canadian income tax on that income.
If you already have been taxed on that income in another country, you can declare that on your Canadian income tax return. In most cases, tax treaties will protect you from being taxed twice.
If you sell a foreign capital asset once you're living in Canada, you will be liable for capital gains tax on the profit that you generated between the date you became a tax resident of Canada (usually the date on which you landed in Canada) and the date that you sold the asset.
In order for you to know what that profit (or loss) is, you need to have a documented fair market evaluation of that asset at the time that you became a tax resident of Canada.
This is explained in more detail in the following Wiki articles:
Capital Gains Tax-Canada
Foreign Asset Reporting-Canada
Tax and House Sales - This article provides detailed information about moving to Canada and moving away from Canada. It is essential reading if you're going to be selling a house in either scenario.
 Income tax
Please note that all people who are deemed to be residents of Canada for tax purposes and who are liable for taxes must complete an income tax return.
This is true even if you're employed, and your employer deducts income tax at source through a Pay As You Earn (PAYE) system.
In the year that you become a tax resident of Canada, the Canadian government taxes you only on the income that you've earned after after becoming a tax resident of Canada.
For more information, please see the Wiki article on Taxation.
 Child tax benefit
Please see the Wiki article on Taxation.