This is a list of videos that I belive are helpful in developing characters and character backgrounds. Not just for Role-Playing Games, but also for characters in written works. I think this is an underappreciated element in Tabletop RPGs.
6 Questions You Should Always Ask When Creating a New Dungeons and Dragons Character
D&D Players, Please Make an Adventurer! Don't Be a Harry Potter!
Avoid These Dungeons and Dragons Characters Mistakes
Build Better D&D Characters with Superstitions!
The Worst Character Creation Taboos for Dungeons and Dragons 5th Edition
How to Fix a Boring Dungeons & Dragons Character | Player Tips
How to Avoid Dumb Character Backstories – Player Character Tips
Making an Awesome Character in D&D 5e
How To Use Traits, Ideals, Bonds, & Flaws In Dungeons & Dragons 5e
How to Avoid Terrible Roleplaying in D&D 5e
How to Run a Session Zero for Dungeons and Dragons 5e
Life is Like a Box of Chocolates | Call For Aid | Taking20
10 tips for shy roleplayers
How to give your D&D character a personality
Backstories don't have to be tragic to be interesting