P r o f e s s o r F l i t w i c k ' s H i t - t h e - D o t Swish and flick, remember, swish and flick. And saying the magic words properly is very important too.
Hit on the dot as they are selected randomly by the muggle contraption. 1 point per hit, minus 1 point per miss.
Test your skill. How many buttons can you hit in 30 seconds?