1. you shouldn't make your character's life story right away. take the time to play out the character, and understand the direction you intend to go with them. as you mold into playing your character, come up with a back story for them. i think my absolute favorite thing to do, is write down a basic life story for my character. then later on, as i play the character, farther down the line, i'll write lore stories about their past, in order to shed light on why they do certain things/why they act a certain way.
2. varying on the direction in which you intend to create your character, think of what you plan to incorporate into their future. say they were apart of a war, will they still feel the effects and trauma of it? say they fell down a well as a child, will take make them afraid of water, or holes in general? think of it in a basic sense. these things /could/ effect the character in the future, or perhaps, not at all.
3. try thinking of how their personality affects other people's lives. are they rude, or generally rough around the edges? will they hurt other's feelings? it's in that way you can figure out how they will affect their own lives. it's more often than not that a kind character will be treated kind in return, and a not go kind character being treated terrible in return.
i hope this helped :>