If you ask for advice on what kind of OC to make, people will tell you the obvious. "Make sure he/she isn't perfect." "Remember that unless they have a job or come from a rich family, they can't afford 1000 outfits or all kinds of expensive goodies." "Give them personality flaws so readers can relate to them."
But there's a lot of other things people forget when it comes to creating OCs as well. So let's list them out!
1. Look at all of your original characters. How many of them are NOT Caucasian?
Seriously, think about it. It seems like OCs come in three colors: white, tan, black. We're all guilty of it. But the world is so diverse, and it's time our characters are, too! Try researching nationalities that you know little or nothing about. Create a guy from Spain. Or a girl from North Korea. How about a Brazilian, a Kenyan, or an Irishman? Look up the norms and customs of these places and incorporate them into your character. It's actually a lot of fun!
2. The world is apparently 90% teenagers.
Most OCs seem to be between the ages of 13 and 25. "Well, my story is about teenagers! Didn't realize it was illegal to have teenage OCs, gosh." Don't worry- I'm not criticizing at all. Teenagers are the most versatile of characters, because they're still growing and learning about who they really are. They're easy to write about and are easy to relate with because we all went through their problems. But why not introduce some of their parents/grandparents? Or why not just once in a while write a story about adults? Or really young kids? The versatility is good practice.
3. I like big butts, boobs, etc, and I cannot lie!
Female characters always seem to be either super busty, or totally flat-chested. You must realize there are several bra sizes, typically ranging from A to G. A girl in a size B bra still has boobs, so don't draw her without any. If you're not sure how big or small to draw the chest, just look at your female peers. You'll realize that there's tons of chest sizes, and hey, you get to look at boobs. (This also applies to butts. Not all girls have big butts.)
4. So do your characters live in the past?
How often do you see characters, especially the teenage ones, texting, on their laptops or tablets, or playing their DS? Pretty much NEVER. The few times I do see characters in comics using technology, they're usually on a giant dinosaur PC computer or using a flip-phone. Technology is a HUGE part of the world now- utilize it! Make your character join an online dating site, or have one of their personality flaws be that they're addicted to texting/facebook. You could add whole new plot-twists or chapter ideas based around the technology of today.
5. Facial expressions and ways of speaking. Are your characters clones?
The final and probably biggest thing I see in almost all comics/stories is that every character seems to act pretty much the same way. They all use the same slang words and have the same basic facial expressions. Don't you think it's time you added something unique to these OCs? Maybe that really tall kid walks with a slouch because he's self-conscious about his height. Perhaps that quiet girl has a bad habit of biting her nails or chewing on her hair? And maybe the geeky kid is a little OCD and is always adjusting his glasses. Your characters may LOOK different, but if they talk and act the same way, they may as well be all the same character just wearing different costumes.