When some one is teaching you a new game there can be a great deal of information to remember. This is when a players memory aid can be very useful. Simply write down a condensed version of the rules that the players can refer to while playing the game. I try to keep it to the rules I am confident will need to be looked up during play. For example the players aid for Schnapsen shown above has the ranks and values of the cards and how to score the hand. For a game like chess you might chose to put the moves of the piecs on your memory aid.
If you have some ideas on what make a good memory aid for a game please share them in the comments.