boing, in general, common sense will tell you if you're storing them in an unsafe manner. You've already hit some of the main points.
The list of what not to do is probably shorter than the various methods you can devise to store them safely:
Don't store primers and powder together.
Don't store more than 10,000 primers or 20 lbs of powder in any one place.
Don't store primers in a tube or in any device where they can all explode if one goes off. (IOW, store them in the original container.)
Don't store PorP where pressure can build up if they do go off. That is, don't store them in a safe or any thing like that. A lockable wooden cabinet is recommended. I think a thin gauge steel filing cabinet would be safe since it will bulge sufficiently before pressure can build too high. I have seen folks use an old unlockable refrigerator or freezer (it should have a magnetic door seal, not a latching handle).
Other than those major points, I think you can store P&P just about any way you can devise in your particular situation.
I have left out the 'out of reach of children' and environmental aspects (heat and humidity) since they don't have to do with the direct safety issues of P&P. They fall under the "common sense" rules.
