Have a look at the questions on the file in this link.
http://www.ece.ualberta.ca/~jgill/documents/immi/interview_S_F_class.pdf
You should be comfortable answering any of these questions. Also, make sure you review with your wife the application you submitted, so you are familiar with all the information on it.
Remember, these are not trick questions, these are questions designed to evaluate how well you know your spouse, how well you know each other's circumstances, how genuine is the story you submitted of how you met, how your relationship developed and how you came to the decision that you wanted to spend the rest of your lives together.
Expect questions relating to the home you lived together in while you were in Canada, questions relating to even intimate things like what kind of birth control you use. I'm not kidding, and don't take the questions personally, the Immigration officer is just doing his job. Remember, they do not believe you have a genuine marriage, so you must convince the officer that you know your wife as a person, why you love that person and that you want to be with her not because she is Canadian, but because she is the person she is. It is not enough to use vague terms like "she's a nice person or a good person", be prepared with specifics from your relationship with your wife.
It is expected you will be nervous. Don't worry about that too much. Also, if your wife can make it to go with you, that would be a good idea. If not, tell her to keep her phone handy. They may not call her, but you never know. Even something as simple as saying, "If you would like to contact my wife, she has made arrangements to be available during this interview today" can cast a positive light on a questioned relationship.
You already know what they are questioning, and you have 6 weeks or so to prepare. Get ready for this interview together, even though you will be the one attending it. Have proof of continued contact between the two of you in the period since you returned to Jamaica, phone bills, MSN chat logs, letters, cards, whatever. Bring photographs if you have any, especially if she has been here to see you since then or plans to visit you before the interview, also copies of flight itinerary/boarding passes.