Just to add to the above...
Don't forget to file an OUTBOUND eAPIS (Canada doesn't care, but the US wants to know when you're outbound.)
Then, for Canada... from 2h to up to 48h before, call 1-888-CANPASS to talk to Canadian customs. You'll have to have your manifest with passport numbers, birth dates, etc. ready. They'll also ask about alcohol & firearms. They'll ask what airport and where on the field you're going to, if applicable (at some airports there's a specific customs FBO or a separate customs "ramp".) If your arrival time changes by more than 1/2 hr, you need to update your ETA.
Upon landing, go to the customs ramp or pre-determined FBO; I fly Canadian registered aircraft so 90% of the time I don't get met, so I won't shut down the engines if I'm planning on moving to park in another area - I just call them from the sat phone or cell phone and they tell me to move on or that I'll be met. (They're not as crazy here about remaining on board your aircraft like they are in the US - you can totally go into the FBO to call CANPASS if no one is there to meet you.) But... as the other poster mentioned, since you're corporate with an N number, you have a higher chance at being met.
On your return, file your eAPIS again (again, Canada doesn't care you're leaving but the US wants to know when you're entering) AND call your destination Customs folks (number in the AFD as part of each airport's info) to advise them... and keep in mind you need to make this call during normal business hours. If your ETA changes more than 15 minutes either side, call them to update. You'll be met by US Customs, usually at the FBO of your choice, just confirm with them when you call, but don't get out of the airplane until Customs says you can.
Some more info here:
CANPASS - Corporate Aircraft: Telephone Reporting
and if you're not a CANPASS member and/or don't qualify, you'll just have to follow these rules, which are pretty much the same except you're restricted to certain airports/times for entry into Canada:
Customs - CANPASS
But I would recommend calling the CANPASS folks well beforehand and just clarify things... better safe than sorry!