I can't give out any tips because I myself just started writing. I base my style of writing around freeflow, basically I created the races, names of characters, and gods/goddesses. Starting from there I imagine what those said characters look like and what type of personality they have from all those pulled together.
My character i'm focused on now Calatros (not my main character), may seem nice on the outside, but in his inner thoughts he can be very critical of others at times.
The character i've made and like the most right now, is actually a side character named Veltak. Who comes off as stiff on the outside, but his inner thoughts show that he actually cares for others a lot and can joke when he wants to.