1. Press Control, shift, c, to get the cheats window to open. (Be sure that you are in the neighborhood screen.)
2. Type "BoolProp testingcheatsenabled true" (without the quotes)
3. Then go with whatever family you were going to play.
4. There should be some numbers and letters in the top right corner.
5. If you look at the things that can be moved horizontally (like needs, relationships, etc.) then you can shift that. Just click and drag to the right or left.
6. This cheat lets you do a lot of other stuff too. Press shift and click on things. Sometimes you can do cool stuff with them. Just don't do "Force Error" That's bad...
7. If you shift + click your sim, there will be (among other things) something that says "Tombstone of L and D" Click this. It is very good.
8. Regularly click (without shift) on Tombstone of L and D. THere will be a lot of options, such as "add _____ to the family. Have a baby. Make me alien pregnant" etc. After your sim is pregnant, and you hear the lullaby, wait a few moments. Then click on the Tombstone. There will be something that says "Speed up my Pregnancy." If you click this, your sim will have a baby in a few minutes, as opposed to three days.

I hope these tips helped. I've found them to be VERY useful. Happy gaming!