I'm writing a story, and I'm trying to really develop my characters. What are some ways I can do that besides dialogue, flashbacks, and just talking about the character?

One of the most common themes in character development is the "redemption " of the character. This happens when something which is causing the character to suffer is relieved (i.e. reuniting with family, recovering a lost love, finding a new love, resolving some past incident causing guilt, etc.)

Basically, anything which takes the character's "woundedness" and restores them to wholeness is redemption, it works because it resonates with the desire we all have to be whole again.

Create little quirks that always come out each time a character confronts a similar situation. eg: blushing when complimented etc.

I think the key to developing characters is to think of the little things that make people individuals. For example, a character who says "OMG" out loud instead of saying "Oh my god" has a character trait that makes him or her real. That's one way to develop characters.

Another thing is, their thoughts. I write what my characters are thinking. Emotions are a big thing. Events definitly.

A character I created was a young boy who actually had a carefree life till his family was murdered. A boy who always had someone around him now had no one. Emotions tell who this character is very well. I actually don't give a good description of the character, just his personality but people who've read it have fallen in love with this character cause they feel his pain. They can associate themselves.

In that character development, events was the biggest thing. And as what was said earlier, how they can recooperate after that. Transitions of the character is the best way. Physical description isn't needed as much as people will visualize them anyone. Association is important.

I actually feel sorry for my character as that isn't all that happens. I'm usually brutal to my heroes.

description of the character preferably from someone else's point of view
it's a good idea to do this before you begin to write because you an make it "boring" and then use it to form descriptions of your characters imaginatively
what i do is write " on a stopwatch" that means i am writing to a time limit in the time limit i jot down as much information about the character as possible

example:
Bret Hart is 50 years old he's a retired pro-wrestler Bret likes to draw and enjoys watching the simpsons

the more you write the easier your characters will seem human think aboout all the little things that make them tick

Basically just discover them while writing the first draft and, then, in later drafts put as much of their personality into the story as you can. You should include mostly major things about their personality and not the minor things (unless somehow this reveals the character in a deep way). Also, if you put a character in interesting situations, how they deal with those situations really makes them come alive.

You worry about developing the world they inhabit and their natural reactions to events will develop them indirectly. It also helps to know (at least in your own mind) WHY they would react thusly.

For that, it helps to know the histories of the characters. What is the underlying reason for why they act/react the way they do? You have to remember that they are people too. Fictitious people, true, but a good character is still as complex as meat-puppets like you and I.

Once you get those down, the rest should flow naturally. My experiences have taught me that characters tend to develop themselves after that.