Students can work in pairs and each are given a sheet which looks like this:
Every sheet will have a different infinitive in the middle. You may want to use verbs with the same endings/regular verbs if the class are low ability.
They have to agree on what to write for the first person singular of their infinitive and add this to the top left cloud. Then they pass their sheet on to the next group so that they have a different verb. Now they will do the same for the second person singular in the next cloud and so on. This helps them understand that the rules will be the same for different verbs. Make sure they know who to pass their sheet to and tell them not to pass their sheet on until you say so (maybe you could use a timer) otherwise it will be mayhem. You also need to make it clear that they only fill in one cloud on each sheet because they can get a bit keen and will try and do all the clouds at once. The last group should check the answers are correct.