First and foremost - and I know this one will get me flamed:

BEING MARRIED.
I'm sure I'll get flooded with posts about how many wonderful children come out of single parent homes (and I agree - I know many of them) and how marriage doesn't necessarily make for a positive environment, but I think those cases are the exception rather than the rule.

Other things I think should be required:
-A financial plan, and a plan for how the family will get by in the event of a sudden life change (ie. loss of job, death of family provider, etc.)

-A statement of agreed upon values. I can't believe how many parents have children only to discover that one wants the child to choose a religion for themselves, and one wants 12 years of Catholic school. How can you not discuss these things before getting into a serious relationship, much less having a child? I don't care what the plan is, as long as the mother and father at least know each others stands and can agree upon them.

-Major, major, major councelling. This somewhat goes with the above, but I think two people need to seriously evaluate themselves and each other before procreating. Experience around children should be included in this. Perhaps some sort of shadowing program, for hopeful parents to work with a couple that has children, and learn how they handle children. How many times have you seen someone have children and then say "I don't really like kids, but I guess I have one now" -or- I can't stand my baby-momma, but I'm stuck with her now because of the kid. these are things that should be covered before you hit the sheets.

That's all I can come up with off the top of my head, though I'm sure I'll think of many more things over the holiday.

Note to responders: I'm not going to be back until Friday - so if I don't respond to something directed towards me, it's not because I'm avoiding you. I'll do my best to answer when I come back.