Radio? You must be doing pretty well to consider advertising on the radio, isn't that fairly expensive?
As far as the yellow pages.... it seems to me that using the yellow pages yields a pretty low ROI (return on investment). As a ratio of how much you have to spend to how much you can expect to make, dollar for dollar the yellow pages are starting to seem like a ripoff to me.
Where I live you have to pay $400 a month for a puny ad!

I have the best results with google. Doing my own
seo, I have risen to the top of my area's local search results for "window cleaning" and "office cleaning."
Advertising and marketing techniques seem to have different effects in different areas. If there is an older demographic in your area, the phone book may be highly effective as they tend to use it exclusively. However, if you are targeting the young, high-tech professionals, you need a strong internet presence.
What's strange is that customers coming from different avenues behave differently. Referral customers are usually good ones. Customers that I have gotten from search engine results and that have read my website are almost always great customers for some reason. On the other hand, customers who I have gotten through coupons seem to be very fickle and unloyal
Kitsap Window Cleaning