First of all, you have to create an understanding about the philosophy of the fictional character which you are going to analyse. You must know about the briefs, values, customs, traditions and norms of the character. In this way, you will be able to create an initial understanding about the character.
Then, you have to analyse the physical appearance of the fictional characters. Normally, the good guys are portrayed as handsome men with fit body. However, there can be other examples also. For instance, Hancock played by Will Smith was used to be an ugly but a good buy. On the other hand, the negative characters usually have very bad physical shape. In addition, you must also analyse the cloths of the characters which they wear. Mostly, the fictional characters wear some particular type of costumes. However, there are some characters which seemed like normal human being and had some huge impact on the minds of the people.
You must also analyse the emotional state of the character. What they feel inside their minds? How they feel about their surroundings and how they react towards the activities in their environment? Understanding the emotional side of your characters is extremely important for you as you will get to know the character from the deep inside.
After analysing the emotional state of the character, you have to understanding his stature in the overall society. You should know how the character behaves in the meetings with the people.
You should also understand the intellectual side of the character. Whether he is a genius or a dumb? For example, ironman has been shown as a genius millionaire playboy and Hancock has been shown as a very casual street guy.
You must also create a firm understanding about the social setup in which the fictional character is living.