This can be a writing activity or just speaking.
Make groups and determine student order. Show the picture of the sign and the key words. The students race to complete the sentences. When ready one member will come to a teacher and read their sentence. If it is good the team gets points. For points I either do fastest teams get more points or use random point cards. If I'm doing fastest team gets more points then after a few rounds I add the option of rock scissors and paper with the teacher. If they choice to play they can risk their points. Rather than getting 4, 3, 2 or 1 point they can gamble and get 6 or 0. Really ups the motivation when some teams start to fall behind. After each sign you can do an answer check and then go onto the next one.
It is important to let them know 'no ing' when using 'must'. They will make this mistake a lot with 'You must not smoking'.
Also let them know that spelling is not an issue if you are doing writing.