There are two scenarios at our house.
1. Weekdays where we need to go work. The time to get up is 4:30 a.m.
Under this scenario at no point is there any "waking us up" of any kind tolerated. This includes meowing, stepping on heads, stomachs, necks, jumping around the bed or furniture, or making noise of any kind. In the past, this was a punishable offense which meant being put into the (very large) carrier at the other end of the house until it was time to get up. This time has always been signaled by the alarm clock. After the alarm goes off anything is fair game. They have learned this very well and we haven't had to enforce this for a long time. The carrier now resides out in the garage where it belongs.
2. Weekends or Holidays where we sleep
These days are pretty much fair game as long as they don't start fussing much before 7:30 a.m.
We don't feed them right when we get up, but make them wait until we are showered, dressed, and the coffee is brewing. When the smell of coffee is in the air, it's time to eat, and they know it.