I generally don't use this in really large classes. I find if there are more than 6 groups then there is too much waiting.
Make groups after practicing the vocabulary and the target.
'Math is on Tuesday'
'I study math on Tuesday'
Tell the students to decide a sentence as a group and when they're ready every member should raise their hands. Then together they speak their sentence. The teacher clicks that square on the board revealing the points they get. Then pick another group. Do this until each group has had a chance then start another round.
The points range from 1 to 5 plus a few special points cards. Sunny day doubles one set of points (the next points if they are at 0), Typhoon wipes out that groups points (or best point), happy dance gives every team points (4 for the main and 2 for all the others) and snowy day wipes out all teams points. These are just suggestions.