Don't even think, just write. Write about anything. Anything in the world. It doesn't even have to make sense, wrote about how you feel about something. Write about how you feel about yourself. Just let the words fall in to place. Lose yourself in writing & see what you come up with :) w
Close your eyes for a second and think about what you're going to write. Write the first thing that comes to your mind, write down everything, no matter how lame it is. When you're done, try to put the pieces together.
Expression takes many form depending on the issue at hand and the situation surrounding your expression. Expression through writing should be a true light of your thoughts, ideas and feelings as at the time you are writing.