To develop your character, you kind of have to imagine them as yourself for a while.

Some tricks and activities to get closer to your OC's.

•Rap Battles
•Put Together Outfits For Them
•Write Backstories
•Fill Out OC Forms
•Doodle Them
•Find Theme Songs For Them
•Roleplay As Much As Possible With Them
•OC Questionnaires

[Please Suggest If You Have More?]

A piece of advise - only do one at a time so you can build them thoroughly.