I find that if you start from a normal mill with your legs extended, then once you're on your back you curl and kick you gain a heck of a lot of momentum, enough to do at least a second one even if you're not experienced with baby mills.
The trick I find is that you probably want to roll high on your back, and as a lot of people mention, use your head. It's tough to use your head if you don't mill using your head, but it sure is a really good tip because it works. Gets you started into halos too.
So curl, then kick, curl, kick. Two easy.
Oh, and one more thing, if you combine a baby mill and a suicide you get a baby mill suicide. (duh) It's a pretty sweet move to do, it's one of the first ones I start off with in a battle.
1) Go into a baby mill from a windmill so you get lots of momentum
2) Curl and kick
3) Kick far out and keep your legs out to keep your body rotating
4) Land on your back with your arms out and your legs perfectly straight out.
It's pretty easy to do and it looks awesome. I've included a video clip of my own at home, but it looks horrible because I'm limited with room, and I'm doing it on concrete//cardboard, which is a terrible combination by the way.

Have your fun.
*pappy*
http://pappytas.netfirms.com/temp/babysuicide1.avi