You can try employment agencies which specialise in your field, but most Canadian employers prefer you to contact them directly. I would take a look at which occupations are in demand in the different provinces, and try to aim initially for a province which suits your skills. Then I'd search for companies which are hiring and send them CVs, follow that up with phone calls. Probably book a few weeks' holiday to Canada to and try to get as many interviews as possible during that time period.
Any employer offering you a job will have to either
1) Apply for an AEO (Arranged Employment Offer/Opinion) - they get permission from the government to offer you the job, proving that no Canadian was suitable which usually means advertising the job for at least 2 weeks in the past 3 months. Once you have the AEO you wait in your own country whilst your PR application goes through.
2) Apply for an LMO (Labour Market Opinion) - same deal in that they have to get this from the government and prove that they have been advertising, but the LMO will allow you to get a TWP (Temporary Work Permit) so you would start work in Canada and apply for your PR from within Canada.
Best of luck.
Wayne.