Hey Varg, I have been doing this for about 9 years so hopefully this will be some good advice for you.
For those of you who write fiction from an outline (or at least a mental one): Do you flesh out your characters before you start writing? If so how do you go about doing that?
As far as fleshing out a character goes no. I tried and failed many times at this over the years. The solution I established with all my characters was simple.
Name the character. Pick a name that suits your character not just because you like the name but because of a meaning of a name. You can use a name meaning to build the type of character you want. This can give you a backbone and allow you to take or leave the pre defined information about a name.
Pick the Gender that best suits what you want to achieve but give yourself both a male and female option and start with both in mind unless you are set on an idea.
For those of you who don't, how do you prevent your character from growing (I cannot make a static character to save my life) in a way where they would not act in a manner the outline requires?
I am trying to create an outline for a story (in hopes it leads to me actually finishing it), but I am concerned about characters changing in a way I don't anticipate. For instance, Rika from Wet Cement is nothing like Carol, the name of the original girl in that position. Carol changed in ways both by her experience and historically as she had to pull things from her past to get through situations. In the end, this meant that the girl I started with couldn't be the girl I wrote about later, since the later girl (now named Rika) has a past and history that Carol couldn't have had and acted the way she did in the beginning. Does that make sense?
I had this problem many times before I settled on an idea. My solution was to forget the characters and write the plot. Start with the ending first, its okay to change things and ideas along the way as long as you push towards your end goal. Give yourself a story outline of thing that you want to achieve along the way. For example.
The plot for character
is realizing that they are really a ghost.
This opens up the questions you need to answer the plots questions.
Who did character
interact with and did they have anything to do with it
What happened to Character
Where did the even that made character
become a ghost
When did this happen to Character
Why is character
This is still not a fool proof system though. You can go back to the start and pick a name and events to suit what you want in your story. But naturally your characters will grow. They will grow with you and the more enthusiastic and passionate you become about a character and the world they live in the more the character will grow. The Difficult part is not chasing the 'Plot Bunnies' As my wife likes to put it. The way I avoid this is setting a specific theme for each chapter. The theme will keep you on the straight and narrow. Avoid chasing unwanted side plots unless you believe they fit into your story line.
From personal experience (Look at what I wrote in the cold heart thread) everything will change the longer you give it. I personally started with an unnamed character, she was Gifted the name Gina and had a partner named Darnell who ended up dyeing and haunting her never wanting to leave. 9 Years later the two characters are still part of the story but everything changed. Now they are enemies and have their own problems to deal with.
To have a character act differently from an original character their is a nice little way around it. Work a split personality into the story. Its a good plot device.
Let me know if this helps.