There is always "regular" advertising; newspaper inserts (some success lately), the YP, postcards to high-end residential areas.
Some non-traditional avenues to pursue are:
Contractors - Even if a contractor covers a new tile floor after installation, the paper never seems to last long and rarely gets replaced. The floor is walked on and gets dirty. Sell a quick clean - and seal if necessary - before the house is delivered to the client.
Floor covering stores - Partner with them to offer their clients a free cleaning within a year of purchasing flooring. Give the store a good price so they are still making money from the sale. The store can promote this to help sell flooring and it gets you into the house of a potential client. A good way to create a repeat client when they see the difference your service makes after even a year. Goes for carpets as well.
Tile installers - You can sell them on color sealing pretty easily if they have ever had an install job where the grout was not the correct color or the client just didn't like it. Again, you're creating a win-win situation. You're helping the installer keep a client happy and saving him a lot of aggravation and the cost of potentially having to regrout the installation. You have the opportunity to interact with a potential client by doing a color seal demo to help them choose the correct color. They are also a good referral source.
Craigslist - A lot of people look at CL to find local services.
Once you get into a house, do a color seal demo. If you can do this, you'll sell the color sealing 90% of the time. If you don't already have it, order the salesman kit from Grout Perfect. Use a small plastic tool box (like a tackle box) and add to it a bottle of cleaner (I use Klenzall), a bottle of floor stripper, a grout brush, and some toothbrushes for applying the color seal. The cleaner is used to clean a couple of grout lines on which to put the color seal and the stripper is used to remove it. The box keeps everything organized and sets a tone of professionalism for the client.
I'll email you a recent insert that worked OK.
Hope this is helpful.
