Not too much.
You should have all your docs ready i.e. your Letter of introduction (approval for work permit) from CIC, evidence of being spouse like marriage certificate etc. Your spouse's LMO, work permit, if already in Canada, may be carrying a pay stub or two along is better.
You should know your stay in Canada is TEMPORARY and have your spouse contact number, residential address and preferably his / her employer's details with you.
Some of this would be extra and probably not needed, but it would make your experience easier and simpler.
In general CBSA is very happy if you produce all needed documents (since people often don't) and would make stuff much easier for you.
If you not landing in the city / province your spouse is working / approved to work at, you should have a legitimate reason for landing at another location.
They might be suspicious that your spouse is actually working there and you intend to live at the same location too. Explanations like getting easier flights, having relatives to initially go to (in which case you should have contact details of them) would be sufficient.
Lastly, make sure they write the correct city on the work permit. Else you would have to go through pains of correction and paying 1500 CAD fee.
I have seen people destined for another province landing in Toronto because they had relatives there. CBSA officer says "i would give you approval to work any where in Canada" which is not true - just a mistake on CBSA guy's part and writing Toronto on work permit, which technically invalidates it since you were not supposed to work there. It should always mention the city of your spouse's actual work permit (if you have any)