I'm not the greatest writer in the world. My skills need some serious development. People aren't breaking my door down begging for advice. But I do strive to make my work as unique as possible, especially when it comes to OC's.

I try to create a character that will enhance the canon, not destroy it. Crack fics are an exception to that rule. Otherwise, if you want to pair your OC with a canon character then you should make sure their personalities are compatible. Some types just aren't meant to be together. Anyone who thinks otherwise...Yeah. (ノಠ ∩ಠ)ノ彡┻━┻

What's in a name?
Names can be important when creating an OC. Remember this: Location, location, location. Depending upon where your OC is from or where your canon is set in, your OC's name should reflect that. Don't give a Japanese character an American name. Don't give a character from some foreign fantasy RPG land a Japanese name. Simple, no?

You also want to avoid names that have been overused. The first most overused names I've seen are Sakura, Raven, Melody, Sakura, and Sakura. Almost every fandom I've been into had at least ten fics with an OC named Sakura. ಠ_ಠ

Looks aren't everything.
Actually, they are when it comes to creating an OC. Unless your fandom has canon characters with technicolor hair and hetero-chromatic eyes, you should probably avoid those characteristics when creating your OC. Try to make your OC fit in with the canon. Don't make them plain, but don't make them stick out like a sore thumb, either.

When describing your character in the fic itself, avoid using flowery language and/or ridiculous adjective/noun combos. This includes describing eyes as jewels, orbs, and pools of whatever random Crayola color comes to mind. And you don't have to tell your readers what they're wearing every five seconds. We don't really care.

The difference between a person and a personality.
Everyone has heard of the dreaded Mary Sue. When you create an OC, give them a purpose. What kind of goals are they working toward? What motivates them to do what they do? Why do they say what they say? Feel the way they feel? The possibilities are endless!

Just be careful with what give them. Characters cross over into the 'not believable' territory if you give them too much emotional baggage and they don't handle it realistically. Put yourself in your OC's shoes if necessary. How would you react?

Another important pitfall to avoid is creating an OC that is a carbon copy of a canon character with some slight adjustments. Genderbending your favorite characters and giving them original names doesn't make them OC's. Sorry.

The tools we've been using for the last ten years.
Here are some handy resource sites that I often visit when creating a new character. I hope they inspire you!

Behind the Name - This is a great site if your OC has a location-specific name. It provides all kinds of search options. There are also nifty snippets of historical info behind the names' origins.

Seventh Sanctum - If you're looking for inspiration then look no farther than SS! This site is full of fandom-specific generators that range from story writing ideas to full character profile creation!

Springhole - This site is full of generators and guides about writing. If you need a detailed guide then you'll want to go here! It always helps me. :)

I hope this helped everyone! Good luck with your writing!