Start by reading Leon's first post in the first thread in this forum, it's an excellent summation of the process. You will want to choose Outland for your spousal sponsorship application, they are extremely efficient at processing applications, most persons are through and receive permanent residence in 3-4 months after London receives their file.
The fees for a spousal sponsorship are Cdn$1,040, not including the cost of your police certificates (1 for every country you've lived in for 6 months or more) and your medical by a Designated Medical Practitioner from the CIC list.
Start gathering proof of your relationship, going up to your marriage is a great time to be doing this. Proof of cohabitation, if you've lived together, is a great place to start. Add proof of support, proof combining your lives financially and you're on your way. For more information, read here starting at Section 5.1:
http://www.cic.gc.ca/english/resources/manuals/op/op02-eng.pdf