If you start out as primitive succession where your sons or daughters or both get equal distributions of your titles.....

It is good to know that you can actually disinherit them but it cost renown, does it worth it? Maybe at the starting stage.

It is also good to know that if you have more children than your titles, the law will automate crate new titles to give them.

It is also good to know that while you are alive, you can grant titles to your children (except your heir) to have them "run" counties. These titles for some reason still belong to your dynasty so instead of passing counties to some random npc, try passing them to your children and when the succession come, every titles between you and your children will be reshuffled. Hopefully the combined titles will be more than your children thus your heir will recieve the primary title and some county. Then, you have to deal with the aftermath where they will attempt to coup you due to bad relationship.

Also, it is good to know that you should only have one primary title and that is the strongest title available. For example, "Kingdom" or "Empire". Do not create more than one because it will cause whoever receive them go independent since their biggest title is equal to heir.