[Mr Sparkle]

Hi guys i've been doing domestic window cleaning for about five years now, Think the time is right for me to go into commercial window cleaning, Just want some advice please

What's the best way to get new commercial work?
Is it best to send letters to all commercial places or is it best to just do some phone calling ( tele sales ) and call all the places and save on the stamps. What's the best response?

Please help me guys