There's not much choice so you just don't sleep. Takes a bit of getting used to. After a while you jump into bed at 10pm when before you had children you'd go to sleep at 2am and become a 'normal person', sort of.

Split the night with the other parent (if not a single parent). Gets you ~5-6hrs/night even during the worst of it.

Trade sleep-in days on the weekend.

A combination of luck (definitely) and technique (maybe) can have 'em sleeping through the night in 2-3 months, so it's not necessarily a long-term problem.

I'll second baq here - I used to be someone who went to bed sometime between midnight and 1am, then rolled out of bed about 9am, and started work about 10. Now if I feel really daring I might go to bed at 11, knowing at the very latest I'll be getting up at 7am, more typically I'm in bed shortly after 10.