Re: Character Development
Characterization and character development all come down to how believable your characters are. The best way to do this, as stated before, is to make sure that your character has both positive and negative traits to them. A flawed character is much easier to relate to than a perfect character. And relatability is one of the best ways to convey a sense of realism to the audience. If they can identify with the fact that the hero has his/her weaknesses and shortcomings, but still realize that the character is ultimately good, then you've got a bona fide believable character on your hands. Vice versa, if the audience can despise the villain, and yet still perhaps have at least some understanding of where he/she is coming from, it will be much more believable.
All of your main characters should be dynamic. Period. There is NO reason that the heroes and the villains shouldn't make changes over the course of the story, for better or for worse. Often times though, these changes can be lost within the plot. The best way to compensate for this is to throw some supporting characters in who are static. This way, the audience can react to the changes the main characters are experiencing and going through by comparing them to these generally static support characters. Not to say that these static characters should be completely flat, two-dimensional cardboard cutouts. Static characters can still have depth, but ultimately, they will remain the same, and thus should (generally, though there are some exceptions) be relegated to the status of support.
The best way (in my opinion) to make a character change is to change his/her motives and/or goals. What I love doing with my characters is making them have the same goal, but for different motives. For example, a villain is trying to kill the hero because the hero is a high ranking political official, and assassinating them will make it easier for the villain to carry out his/her plan. However, during an attempt on the hero's life, the villain loses something. Perhaps their lover somehow gets wound up in the affair and dies. Now the villain is still trying to kill the hero, but rather than doing it for political gain, they are now acting out of revenge. Of course, there are many more ways to change motive without changing goal, and vice versa. The character may have a different goal, but for the same reason. One of my favorite things to do, in fact, is to have the hero and the villain have the same motive. Let's say peace between two nations. But the way they go about doing it, their goals, is completely different. Where the hero tries diplomacy, the villain wages war.
Anyways, I'm kind of rambling now, but hopefully that helps you out a bit.
Oh, and just to continue as to why Spiderman is a great example of a well developed character: he is in constant battle with himself as to whether he wants to be Spiderman or not. Although he feels the obligation to fight crime, and stop people from experiencing what he experienced with his uncle's death, at the same time, he's not sure if that is worth the loss of his social and love life. If he remains Spiderman, he fulfills his sense of duty, but he also can never be with the one he loves. That conflict makes him a superb, and relatable, character.