You need cut-up slips of paper or card to write words on and an envelope or a box. (The boxes personal checks come in are a good size.) If you tutor more than one group of students, make a separate box for each group.

During the lesson or immediately after, someone should write on each slip of paper one word that was introduced or that students had trouble with during the lesson (up to a maximum of 10 words). (You may do this or a student volunteer can.) You could let more advanced students decide together which words to include in the box. For lower levels, you may want to add pictures to help illustrate the words. You may want to include other information about the word (part of speech, words that collocate or go with that word, etc) on the card.

All of the cards go into the box. Bring the box to every lesson and make a point of spending a certain amount of time each lesson reviewing some of the words. Students can use the cards to quiz each other, for categorizing activities, or as the basis for hangman or password or other vocabulary games.

Occasionally, go through the words in the box with students, letting them discard the words they know and feel comfortable using. This helps them see the progress they are making.

Comments:

It may be helpful to go through the box and sort the words by topic, using paper clips to separate groups of words. That way, you can choose words that relate to each other in some way (rather than random words) to revise during the lesson.