I have not done this particular idea before. It is something I've thought about as I'm constantly coming up with different ideas. I probably only go after 10% of the ideas I come up with and a few fail while a few do really well. I automate those and implement a new one in its place.

Should be really easy to get going though. First step...

Order some sample coasters.

Second...

Go to the bars and say hello and let them know you want to give them something for free. Shouldn't be hard to sell that. Ask the bars some questions like - how many people do you think you serve on the weekends? Weekdays? This will get you some stats to present to potential clients. Same as newspapers tell clients that they have a readership of 50,000 people.

third...

Create a simple site that covers exactly what you do. Of course I will pitch my company here - zerozen, but you can find anyone who can do a good job and knows how to create a site that CONVERTS. Please...do not try to do it on your own. It won't work out like you want.

The reason you want a site... You are going to add the link on all coasters. Who knows what business owners are having a drink.

Next - start going to businesses and letting them know what you are doing. You really want to sell the value. Compare your reach to that of other advertising methods they might be using.

Hope all this helps!