How about these shopping rules:
If "stopping power" were everything we'd all be carrying 18 inch naval guns. Buy the most powerful gun that you can CONTROL.
A day at the range renting different models will cost you from $20 to $60 bucks, and could save you from spending $600 - $1000 on a gun that doesn't work for you.
Vote with your dollars for quality products and good customer service.
When a sales person hands you a gun, step one is to open it up and verify an empty chamber. Step two is to pretend that you might like to have it but don't really need it and the price is 25% more than what you saw it for across town.
When the latest new whizz-bang handgun of the future shows up in all the magazines, give it time to see if it stays in the marketplace.
At a gun show, always shop every aisle before buying anything. I saw identical Ruger hi-cap mags two tables apart. Vendor A wanted $21. Vendor B wanted $40. Guess who got my business?
"Collector's Item" is vendor-speak for "overpriced piece of fancy-a$$ scrap metal".
Ask before you dry fire.
Never pass up a perfectly good $200 Browning Hi-Power just because it has "Paraguayan Air Force" stamped on it (actual deal seen at a gun show). Most surplus arms have had more brushes than bullets through the bore. besides, for $200 you can shoot it till it crumbles and come out ahead.
When responding to a "gun for sale" ad in the paper, DO NOT agree to bring a stack of cash into the home of an armed stranger.
In private sales, whether buying or selling, INSIST on a bill of sale signed by both parties, specifying the serial number. If you're buying, this protects you from people who will sell a gun and them report it stolen. If selling, this covers you if the gun is misused later. Both things have happened before.