There is no such thing as "joint" income tax filing in Canada. Each person needs to do their own individual income tax, although if a couple is married they will list each other as spouses on their taxes, and claim any applicable tax credits.
So in your case, as a US citizen even after getting married to a Canadian, you personally do not have to file any Canadian income tax unless you actually made income in Canada.
However if you get married in Dec 2014, your husband needs to then immediately change his tax status with CRA from single to married. Then when your husband files his 2014 taxes he will do so as married, and list you as his spouse. They will also ask for your Canadian SIN, but since you don't have one he can just put 000 000 000 for this section. They will also ask for your "world" income, which would be any income you made in the US. This will determine your total family income, and will be used to calculate what tax credits your husband will or won't be qualified for.