I love coming up with my own characters and given them all different kinds of backgrounds. Creepy ones, happy ones, traumatising ones, weird ones, troubled ones.

1.
First of all, start with their name. You can be as ordinary or as weird as you want with this. Here are some names I like to use:
Girls:
Nirvana
Athena
Luna
Willow
Lili/Lily
Tia
Danielle
Eleanora
Ellanova
Raven
Jade
Belle
Alice
Artemis

Boys:
Miles
Lucio
Raven
James
Elliott/Elli
Noah
Carter
Apollo
Hunter
Archer
Jayden/Kayden
Julian
Tyler/Ty

2.
Then, you need to think about their appearance. Their gender. What their skin tone is. What colour their hair is, as well and length and style. What colours their eyes are. How old are they? Their height and general appearance.
I tend to mark charts for this:
Male or female:
Eye colour.
Hair colour:
Hair length.
Hair style.
Skin tone.

3.
After this you need think about personality.
How do they think?
How do they feel?
What kind of people are they attracted to?
What are their interests?

4.
Think of their aesthetic.
What music artists do they like, do they even like music?
Do they prefer books or films, or maybe they just like both?
What are their favourite school subjects, if they even are in school. If not, what college or university courses are they taking?
What colours do they like?
Things like these.

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These are some easy steps to creating your own original characters.