Use an electronic stud finder and map out your stud locations before you cut the holes. You can use a pad saw blade in a Stanley knife or just a regular Stanley knife to cut the holes. Use the template supplied with the speakers, push it against the ceiling, go around it with a pencil, then cut.
Make sure your hole edges are an inch clear of any stud.
You may need to "back off" the fixing lug screws a little so that the lugs rotate properly when you put the speakers in and start tightening the screws.
Other than those points, fitting is a doddle, which is why I have bought FIVE pairs of the Yamahas - three pairs in the media room, two more for the living room - and hope to buy ANOTHER FIVE pairs for Muzac service in other rooms in our McMansion.
(McMansion is the American slightly disparaging slang for a large, cheap, house. We have a 5600 sq. ft. home, but it's all wood and stucco. The philosophy is that you can't economically build houses to withstand tornadoes - and we had four touch down on the other side of Houston yesterday, so why bother with bricks and mortar? Four real bricks - I counted them - in our whole house, and they prop up the gas fire! Flip side is our six bed, five bath, three reception, study, media room, games room and upstairs and downstairs patio only cost half a million quid. Or the price of a broom cupboard in central London. I've got six in the media room ceiling because I started out with a 5.2.2 setup, expanded that to 7.2.4 but left the original two ceiling speakers in place so I didn't have to fix the holes that would have been left if I took them out. I need two pairs for the games room, one for the dining room, one for the master bedroom and a final pair for the master bathroom. Luckily, the builders pre-wired all of these for me.)