2) always unload the gun before crossing a fence
I have to disagree with this. While this is taught in most of the safety hunter courses and sometimes appears as a test question, in the real world, it is not the right thing to do IMO. Reason? Loading and unloading of the gun is the point at which many accidents can and do occur. You're much better off laying the gun on the opposite side of the fence on the ground or against the fence. Then, WALK AWAY about 10 feet and cross the fence. Once on the other side, go get the gun and continue on. If you're with a friend, let them hold the guns while you cross. Then carefully hand the guns over and let the other person cross. Or, both of you can lay the guns over the fence and walk away about 10 feet like mentioned above.
Likewise, I have some friends who debate the merits of unloading the gun when going up a tree stand. Some feel that it is safer to sling the gun securely over the body, leave it loaded and then get into the stand. The theory being a) unloading/loading the gun is a dangerous step and b) that hoisting the gun up via a pull-rope is prone to having several things go wrong. One of which could be making a mistake in unloading the gun. Personally, I'm for unloading the firearm and using a pull rope when it comes to climbing trees and I preach that method whenever I help teach hunter safety courses.