A king size quilt is generally 108" X 108". It will take 36 18" blocks to make a quilt of this size. 6 blocks across by 6 blocks down. This is a very big quilt to make...I personally have not made one in this size. The biggest I have made is a queen. If you are not quilting this size by hand, I truly recommend having it quilted in a long-arm machine, as it is quite difficult to maneuver a quilt of this size around. I have machine quilted the queen size ones in my machine, and found it hard to some degree...especially the middle of it.
If you need any more quilting tips, or are looking for ideas, I have tons of magazines and books for reference. I look forward to seeing your finished quilt...please post pictures if possible.