Choose the set of cards to be used and hold them numbers side up, shuffled. Select the top card. As you decide on your answer, place your card in one of three rows- top row were correct; middle row took a long time to work out; bottom row were wrong. Now you know which ones to concentrate on.
Let someone else test you, with others maybe as well – keep a written record of how you perform. In class this is often how it works, round a table with students of similar ability.
Place a selection of the cards, numbers side up, in any order in an array. Take it in turns to select one according to verbal instructions, for example: