Cutting a watermelon has usually been a pain for me. When I was at the farmers market one day, I learned this simple way to cut them.
Cut the ends off of each side.
Stand the watermelon up flat and cut the rind off in a downward motion.
Cut off any remaining white part.
Your watermelon should now look like this.
Cut it down the middle in half.
Lay it down, then slice it across.
Slice it perpendicular.
You can cut it up again or enjoy it as is.