Make sure that you buy lots of ammunition for common calibers of guns. .22 short, 9mm, .45 ACP, and .357 magnum since all will be used as currency. If you have a farm or a large amount of land and use up ammo, I would recommend getting a reloading kit and smokeless gun powder. Also stock up on lead, silver coins, quality canned goods and dehydrated meat and have a large supply of fresh water.
If things get really bad, you can always hunt deer or large dogs for food. I don’t recall which breeds of dogs taste best.