I'm a novice crocheter so the afghan is made from simple granny squares. It was a great project to carry around. I worked on it waiting at music lessons, chess club...as it was so portable. The squares are joined with single crochet stitches. I searched on line for a way to edge it, and am sorry to say that I cannot remember where I found the instructions for this.
First I crocheted around the entire afghan using a single crochet in blue. Then I chained 5 in blue and joined to the afghan edge with a single crochet. I believe I skipped 3 single crochet stitches in between each arc. Once I finished going around, I joined the beige yarn and repeated the procedure, only this time joined with a single crochet in the middle of the previous arcs formed. The final finish was the shell stitch in each of the final arcs - single crochet, half double crochet, double crochet, HDC, SC. I love the way it finished it off - almost lacy.
Since I had some of the beige left over (I had purchased this) I decided to make a pillow top as I didn't want to add back to the stash. The pillow top is just a big granny square (18 inches) and is finished basically in the same way I finished the afghan, only I didn't use the shell stitch in the outer arcs as I ran out of blue yarn.