Same as felix... Use a hairdryer to heat up the glue and then gently (read: immensely slow) peal it off.
Be careful not to overheat though, it could damage the paint.
Best result is when the bike is new (fresh glue, no colour differantiation)
As said, the kawasaki logo is painted and non-removable.
To get excess glue off, use a soft detergent and have lots of patience. Don't rub too hard, it will scratch the paint.