I think technically, it should be lower case (not capitals) and if it is part of a sentence, then I would keep it that way.
If it's part of a heading on a leaflet, then I would use initial caps (every first letter is a capital letter), to add emphasis and to make it easier to read.
I used to do graphic design, copywriting and proof reading for a living.
If you have something to be proof read, send it to me at
robinsonswindowcleaning@gmail.com and I'll be happy to have a look it for you.
Robbo