The biggest difficulty is when you have an externally imposed irregular schedule -- flying through time zones regularly, waking up for maintenance windows or other night operations, plus going to all-night parties.
The "get up at a fixed time" is the best way I've found to deal with this, but the problem is I am definitely below normal functioning on some days. Driving when sleep deprived is probably a similar risk to driving drunk, so there are times when waking up at 0546 after going to bed at 0400 means the best course of action is to take a taxi, work from home on tasks where you can't break things, or just take the day off to play games.
The "get up at a fixed time" is the best way I've found to deal with this, but the problem is I am definitely below normal functioning on some days. Driving when sleep deprived is probably a similar risk to driving drunk, so there are times when waking up at 0546 after going to bed at 0400 means the best course of action is to take a taxi, work from home on tasks where you can't break things, or just take the day off to play games.