hi! So i figured this would probably be interesting to talk about.
I've learned how to design my characters by hand via breaking down and studying characters in video games (Megaman, pokemon, azure striker gunvolt etc., etc.,).
But that also means i've developed my own unique way of designing characters! I put my own beliefs and rules into the design process. Heres a rules I follow, please keep in mind this is MY way of doing things.
1. Throw gender stereotypes out of the window (mostly)
I work with a lot of transgender, nonbianary and male/female OCs that just kinda..develop their own style. To me its realistic, not ever female in the world looks all pretty and girly, not all males look masculine. I also tend to ignore 'feminine' and 'masculine' applying to certain gender, in my eyes anyone can enjoy make-up, or lifting weights.
However I do like to follow stereotypes sometimes- if the character themselves dresses like the stereotypes.
2. Silouette and Shape are of the utmost importance
I know this is probably a general rule of thumb and I like to stick with it.
You may notice I upload art pieces known as 'colour sketch', their basically sketches I colour until I get the feeling or emotion I want.
Unique silhouette really makes things diverse! it adds in a lot more elements than you'd expect. A human character who associates with cats could have a bow and a ponytail that looks like ears and a tail!
It also really diversifies your cast, a fat character could easily have a different silhouette than a skinnier person does.
3. Never use pure black or white
HEY SPEAKING OF COLOUR
I'm not sure why I developed this- I learnt that you generally shouldn't use it for shading but it leaked its way into my designs. Over time ive found you can put some much better colours there instead.
Instead of pure white eyes you can do a darker grey and make them more intense, or a light blue and make them really stick out while using white highlights without them disappearing into your eye whites!
4. Make sure the design is 'out there'
To me, personally a good design is one you can remember after looking at it even a little bit. People can stop looking at it but keep it in mind, they can even easily recognize and remember the character.
Give the characters a personality, make them sparkly, hell just make em out there. People will remember your design more than those generic sameface characters you see in unheard animes.
5. Shapes don't define gender
this was something I never thought about until a classmate though two of my cis male characters were female in collage.
Its because they were designed with soft, flowing, round shapes (Their themed after beauty and grace and I tried to make them look a little like statues).
I was confused at first before they told me "Oh usually female characters are soft and round and males are square and hard".
I...completely forgot that was a thing. I was so caught up in my first rule I didn't even think of it.
I don't really get the shape thing myself- characters can be much more diverse when you give them any shapes regardless of gender.
I think thats uh...the staples. Yeah, now you know how to design Ruby style! (sort of I could get much deeper and write a long, long essay)