Put the class into teams.
The teacher shows a team a photograph or drawing and the team must each write down one letter of that word (without showing their teammates), depending on their position. The leftmost student writes down the first letter, the next student the second letter, etc.
e.g. the teacher shows a group of five students a picture of an apple.
The leftmost student writes down “a”, the next student “p”, the next student “p”, the next “l” and the rightmost student “e”.
Give them a short timelimit (ten to twenty seconds depending on their English level) and then have them all reveal the letters they wrote. Award one point if the word is correctly spelled, then move on to the next group.
As preparing a lot of words all the same length (e.g. you have teams of 5 students each: it can be hard to think of lots of 5-letter words without going outside the students’ knowledge of vocabulary) you can have words `wrap around`:
If you give a six letter word to a team of five students then the first student has to write down both the first and last letters.
Sitting the students in a ring can help them get the idea.
Making the vocabulary relevant to a current event is of course best (Halloween, Christmas, New Year, Valentines’, etc)