Wow, this is really a loaded one. I have lots of advice to give. Specifically relating to changing diapers, birthing pigs, sweet-talking Sheriff deputies, throwing people off wave runners, getting a herd of kids ready for church, etc.
But I think I'll take the serious route. Not that all of the above aren't serious....I do indeed possess vast professional and all-encompassing knowledge on those subjects, however this one piece of advice may be more practical for most people:
Now let me clarify just a bit. I know all situations are different. But to whom I am speaking are those who are in situations where all the pieces are in place, so to speak. There will always be something, some reason, or some plan to postpone having children. Don't let that stop you. Don't wait. Yes there will be hardships and struggles (heck, just read Day 1 if you need an exhibit A), but your life will be so full of joy and blessings that you won't even remember why you once thought of putting it off.