Decide where your Sailor Scout comes from--this will determine your Scout's name. The best location to choose may be a planet or star system in a far-off galaxy.
Give your Scout a primary source of power. This is usually something similar to an element or emotion; the original Scouts draw their powers from ice, fire, thunder and love, for example.
Come up with a main method of attack for the Scout. The attack should be energy based, created by the elemental energy within the Scout that then takes a specific form. Examples include fireballs, lightning bolts, waves of ice and beams of love energy. Your character's powers can evolve and take on new forms over time.
Create your Scout's back story. In many cases, a Sailor Scout is actually an Earth girl with the spirit of the Sailor Soldier awakened within her because of an intergalactic villain or other threat to the planet or even the universe. Or, she comes to Earth directly from her home galaxy because of that threat, which has likely destroyed her own galaxy.
Draw the form and appearance of your Sailor Scout. You're basically creating a teenage girl dressed in a magical girl costume that includes a naval collar with a large bow at the front and a short, frilled skirt with a bow in the back. The suit is mainly white with the collar and bows displaying two contrasting colors like red/blue or green/pink.