Leveling your Familiar
There are two ways to add levels to your familiar. Improving your familiar is about sacrifice and connection. You are connected and you give your familiar parts of you to make them stronger and better.
Important note about the level of your familiar. Except at levels 1st – 3rd your familiar must always be at least three levels below your character level. So the first time you can start to add a level to your familiar is when you reach 4th level.
Experience Points
You can decide to sacrifice experience when you gain them, and give them to your familiar instead.
Feats
You can take the feat: Familiar Gains a Level. When you do, they gain just enough experience points to gain a new level.