We've advertised on local radio since January and have had probably the busiest 8 months since we've been going,
It isn't cheap though and wouldn't recommend it for new start ups, it's still only part of your marketing mix and most of our customers know if us anyway so is more a reminder to them , our ad is used to drive people to our website and normally they will contact us from there,
Think you'd have to at least do it for a year before you know what real results you are getting from it
Regards
Steve