Hello Caterina! Welcome to the club, erm, thread.
I also have a few tips right off the top of my head (since I'm at work, hehe)
I'd like to do something more detailed later, though, in a more organized fashion.
Do's Design your own Wonder Child after deciding on the careers of your founder and spouse in advance. Just picking a different spouse can vastly drop the difficulty.
Check out the available Wonder Children available for download on the Gallery. I've already downloaded 3-4 I want to use so I can plan ahead for children's careers
This one's great because you can do it away from the computer when you want to play but should be working (I'm looking at you, Wolfie, lol)
Make sure your Wonder Child has maxed the useful skills. Because you start with the lowest-quality furnishings, Handiness is a must-have and can also be mentored.
Buy the Buyers Beware or Ornate Beauty Storage Chest!!!!! You can store all fish, fresh or foul, in the chest. How did I not notice this until two days ago? It's awesome!
Plan pregnancies on a 4+2 schedule to avoid being fired for missing work or missing breast-feedings. The "Eating for Two" notice comes 24 hrs after conception and delivery comes exactly 3 days (to the minute) after that (4 days total); the infant ages to a child exactly 2 days later at the same time.
Don'ts Don't place a grill in your house. Once you place a 1x2 grill in your home, it's stuck there until you clear Bodybuilder.
Don't let your eyes stray from Family-Oriented sims when you have a baby. They will (try to) autonomously bottle-feed a crying baby.
I'll stop here before I start obsessing...too late!