There are some people who need to have colonoscopy (e.g. first degree relative with colon cancer, Inflammatory Bowel Disease, etc. – see resources below) and there are some other tests out there (e.g. virtual colonoscopy, flexible sigmoidoscopy) but for most of us the first option is FOBT – aka Fecal Occult Blood Test aka Mailing Your Poo.
Have a look at this helpful how-to movie from U of T explaining the details of the FOBT test.
Here is the bigger picture from the Ontario Ministry of Health and Long Term Care.
And below are some more great resources to help you understand your options: