I have a lot of plans that carry over from other years. I play Sims on and off, I will play nonstop for months, and then drop the game for months. I am also still in my first two generations of Sims. So my goal for this year will be the following:
Have no more 1st/2nd generation children with the older Sims, except if they are single, and then limit the baby to just one a family.
Start pairing up the teens, and combine families to reduce the population for the 3rd generation, and only let the chosen heirs have children for 3rd generation.
Have non heir sims explore the worlds that they don't live in, and become part of the supernatural, like vampires. Vampires will move back to their original homes in case the heirs family die out or if their are no longer any current offspring to claim the house. Some supernatural Sims may have children of their own, but they would be considered a separate line to the original family.
Age the young adults and adults into their next stage, whether with aging on, or not. Keep the families together, and either retire the parents, or have them live with the family, but not solely as extra caregivers.
Not to create new families unless a separate save, or if the current population drops or is has too many relatives.
For saves with one family they will start into their 1st/2nd generation, and the following ideas will affect them too. However, their 3rd generation will have the heirs with 2-3 kids, while the spares will have only one kid.