I assume you have watched Grey's Anatomy, or are familiar with Ellen Pompeo if you chose her as your person. So I will help you answer these questions, but you should write your answers based on what you think of Ellen Pompeo in your own words.
Character's Speech: Find a snippet of Ellen speaking, and think about how she sounds, the words she uses, and the way she speaks. This can be a piece where she is acting, or outside of a show, when she is in an interview or accepting an award - something like that. Does she stutter? Is she eloquent in her diction? Does she gesticulate (use her hands to speak)? Is what she is trying to say understandable? Does she mumble? Does she enunciate? These will help you in your characterization.
Character Thoughts: There is a difference between Meredith Grey and Ellen Pompeo, which I think here is very important. Make sure that when you are doing this assignment, you do not confuse the actor with the role she is playing. For example, you will not know what Ellen is thinking, since humans cannot read minds. However, Meredith Grey starts nearly every episode with a narration of her thoughts, which is helpful in understanding what she is thinking. You might be able to find examples of Ellen talking about what she thinks about certain issues, which you can complete this part of your characterization with.
Effect on Others: Ellen appears to be much loved by her fellow actors on the set of Grey's Anatomy, so this should tell you a bit about her personality and effect on others. In interviews, observe how the other people in the room act or react around Ellen, specifically to what she says or does. Do they shy away from her as if they are trying to get away from her? Are they laughing near her or smiling? Do they lean in to her? Body language can tell you about a person's effect on other people just as much as speech can.
Character Actions: Again, note the way Ellen acts. Does she talk with her hands? Does she hug or shake hands with people? Does she slouch, or sit up straight? Actions are not just about body language though, so note things she does in a broader sense as well. See if she is a philanthropist at all, or if she supports certain campaigns and takes actions in that sense.
Character Looks/Appearance: This should be the easiest section, as it is pretty straightforward. Note what Ellen wears, makeup or clothing or accessories. Note how she looks physically - she is very petit, so you might write that down. Note also how she appears emotionally - is she happy, serious, or angry?
Hopefully this is helpful, however I think I can help you more if you can change your character Meredith Grey. The problem with choosing a real person is you don't have the inside look into that person's personal life like you do with a tv or book character. This might not be your assignment's instructions however, so don't bother if it is not. Let me know if I can help further!
