Get a bag and some armor. Then put the armor on and enter the bag. Take the armor off and put it back on again. Repeat to build your armor class.

At the beginning of the game, put on your armor in the Inventory room. Then take it off and leave the Inventory screen. Return and gather it up again.

With ammunition in hand (not the weapon), enter combat mode and shoot an opponent. (The response, Did yo mamma teach you that move? confirms correct entry.)