You can start locally by designing an attention grabbing flyer about your coupon club to get people interested. And then those that are interested can sign up or contact you for more information. Your going to have to decide on the general way that your club will operate - meaning will there be gatherings, how will the coupons be traded and what coupons will you be dealing with?
Remember that you will be trying to attract advertisers and don't limit yourself into thinking that the advertisers that you seek will be the products on the coupons. How about one of your club members that is going to have a garage sale? What about a member that does babysitting? Your advertiser base can also include those that are not members but are local businesses and others that know about your club and want to advertise. You can also take advertising from those that want to buy something who are having a hard time locating what they want. I remember reading a story where a guy wrote that he was selling his boat. He got a buyer but what was more interesting to him was the fact that he got so many calls from people who wanted to buy the boat. So what he did was buy more boats and then sold them to the people that wanted to buy them.
You can even expand your business by including Ebay where you can find either buyers or sellers who are interested in Ebay. You can act as their middleman (or woman or person). Ebay has a name for this and it is called "Trading Assistants" which is what you would be.
Even though I had often recommended this as a good business to start I was re-reminded of it when I was reading a blog. The blog is called: