Foreigners wishing to work in Canada must apply for a work permit, either as a skilled worker, a temporary worker or a provincial nominee. In most cases, you will need to submit your application before you arrive in Canada. You have a much shorter wait if you can qualify as a sponsored applicant, or have a job offer that you have obtained from your own efforts or through the provincial nominee program.
As of July 1, 2011, you may only apply for a Skilled Worker visa if you qualify for any one of the following categories:
In most cases, if you have an offer of temporary employment, you must apply for a temporary worker visa. You may also bring your spouse or common-law partner and your children. Each family member must submit separate applications for temporary visa status. If your spouse or common-law partner wishes to work, he or she must also apply for a work permit.
Your employer must obtain a letter from the Human Resources and Skills Development Canada stating that employing you will not cause an adverse effect on the labor market for eligible Canadians.
See here for the list of documents along with the applicable fee.