All of the above is good stuff. Tell them what you have, and your purpose of your trip. Open all your windows as you pull in to the booth, no radio, eye contact, have your passports/documents ready, and let them be the boss (don't be grouchy). Don't be in a hurry, don't crowd the vehicle in front of you while waiting, don't jump lanes, and DO NOT ENTER THE BOOTH UNTIL THE CAR IN FRONT OF YOU HAS EXITED - they really get upset with that one. I live at the border, and frequently am traveling back and forth. Never with hunting equipment, though when I inquired about it (pre-911), even a compound was no problem. There are 800 numbers for customs, and I suggest you try and talk with them early on to resolve any questions you might have. Specifically the location you are crossing at (check US and Canada - so you know what to expect coming back - the US is tougher than Canada)
On a funny note, don't have any Grateful Dead (or other controversial) stickers on your vehicle..... made for an interesting crossing that day....
Others have done this, and I assume they will chime in soon.