Stretches to do for comfortable lotus position?

[Popinjay]

I'm trying to get into zazen meditation and want to be able to do the lotus position. I'm very inflexible and it's practically impossible to get into the lotus position and even when I do it's far too uncomfortable for meditation. I figure if I have a regimen of stretches that I do everyday that eventually I'll be able to do it. So what stretches should I do? Proper names for stretches (for easy googling) appreciated.

lotus position: