In a way I do graph it out - using Visio. I count the number I have of each size - for example 4 pieces that are 8x12 in, 10 12x12, etc. I bought the Too-cool t-shirt book when I started. It has a form in it that you can use to keep track of the different sizes. It also contains a formula for figuring out a starting quilt size based on the number and sizes of the pieces you have cut.
In visio I draw a box representing my starting quilt size. Then I size squares/rectangles to represent the number and sizes of pieces that I have. Then I drag an drop them around the 'quilt sized' box. If there are blank spaces these are filled with fabric leftover from the T-shirts that were used in the quilt. Once I have my layout on paper. I then play with the actual pieces - trying to spread the colors out around the quilt as much as possible. I take a picture of the placement before shifiting pieces around to determine the correct color placement.
Since I also have an embroidery machine I sometimes will embroider the person's name into one of the blank pieces.