I like in-universe explanations and using game mechanics that support my character choices. For example, say I'm building a rogue character that's an experienced assassin, but why would they still be at level 1, or even 3? Maybe they've never actually killed anyone but they're very good at "disappearing" people with poisons and potions, so they'd take medicine and/or nature as a skill. So maybe now we have an "assassin" that secretly helps people flee town by faking their deaths and I see what can be done with potions, herbs, medicines, magic, etc.