Yup I agree with Aspects. Practice is the key. Try and get your neighbors and friends as your first customers. Charge them half what you will normally charge on the understanding that your cleans will be practised on them, then you should have a days work. Us this day to get your method right.
Also, read this forum as far back as you like. WFP is very popular, but traditional still has its place.
Get yourself an Ettore or Unger starter kit (blade, squeegee, rubber, mop, t-bar, bucket, micropore cloths, scrims) and practice on your downstairs with it. Practice your WFP on your upstairs windows.
Make sure you have a Unique Selling Point. What is it that makes you different from the other WC's? Mine is I am uniformed, in a sign written van. This seems to make a difference.
Target estate customers first. Although in my experience 50% of these customers will either mess you about or cancel after a few cleans, they will again allow more practice and allow you to build our speed and confidence.
Canvass regularly, leaflet regularly.
Other than that, best of luck m8