Advertising service as a product is a bit difficult since there is no tangible item involved. You cant touch it, hold it or smell it. Customer satisfaction must be extra high for a service oriented business since negative customer feedback will be disastrous no matter how hard you try to advertise. And if you are running a niche business, word travels extra fast, more so than any other type of business.
You don't have to have a purely service oriented type of business like a car wash station or a Laundromat to advertise service. Take for example my favorite Filipino owned company Jollibee. They are in the food business, but aside from the food they are also selling service. When you enter a Jollibee store. The service crew are friendly and magalang ... Well at least in my experience so far. They work fast and efficiently in getting my order and will help deliver my tray if I cant carry it all in one trip. If I want something like extra napkins, it will only take them a short time to deliver it to me. Now that's what I call service and value for my money.
This is the type of service that I hope most company out there will try to emulate. I know most companies out there don't have the big budget Jollibee spends on its advertising. But if the service you provide is good, word travels fast and a few good referrals from word of mouth will give you loyal customers who would gladly recommend you to their friends and family.