We have a startup, which does accounting for tiny companies. We have successfully tested the service with success for a few customers. These are happy with the service and keep renewing.
Now I am looking for a reference to a method on how to gain more customers. I expect this method to tell me how to choose channels for the initial marketing and how to evaluate these channels.
Things that make me look for such a reference are for example that customers will almost never buy something the first time they see something, but there is a good chance the third time. This is one of the things complicating the evaluation, because maybe the channel was perfect, but no one bought anything because they had never heard of the product before.
I have heard about the bullseye method, which I know was successful in gaining 200.000 subscribers in 4 years to a telecom company, but was unable to find anything anything on that.
As your client base is "tiny companies", your average sale is probably relatively small; therefore you should probably avoid using a salesman to obtain customers. The exception would be if you are willing to pay a very high amount of your sale to the salesman in order to grow your customer base - but just to get started.
A better approach would be to join the local chamber of commerce - assuming your tiny customers are in a local area or areas. Phone book advertising can still be useful. Local small-town newspapers often have business sections that can be very affordable. And make sure you have a useful website - not one of those free pages you often get with a phone book ad. Many tiny businesses still use traditional sources when looking for information.
In a service of accounting, you don't have to sell a new product to a business, you just have to be findable when they are looking. I am always surprised when I look for something and can't find a phone book listing or ad, or a website for a business.
I like Facebook, Google and similar ads. They are cheap and help you target in many ways based on demography, interests, etc. The best thing about this for new businesses is gaining fans whom you can later convert to customers by publishing engaging content. But first, for any business to run, you should have a worthy product.
Word of mouth publicity is also effective. Request your clients to spread the word about your company and write reviews. Offer something extra to your clients/potential-customers which gives you that little edge over established businesses. As you are into accounting, reach out to businesses by phone marketing, drop by to their offices and let them know about your firm. Direct communication is important and it is should be confident enough to convert listeners into clients.
You're overthinking it. If you're really a startup, you can afford to take on as many new clients as you can get.
Go at this from the other direction... look at your existing clients, and see how they're the same, and how they are different. Use this to create a few profiles on who your 'target customer' is.
For example, if you're basically an outsourced accounting department, then I would guess that you deal with some smaller-sized "professional" type offices. Maybe you already have a lawyer or two that you do business with--look for more lawyers, but also look at similar industries that have that same profile of "small business with $XXX,000 in revenue/yr, owner-operated, hands-on, service company."
You'll come up to things like real estate agents, dentists, barber shops, technology startups, small car-repair shops, maybe laundromats?
Then, come up with 3-4 possible channels to reach them with. How you reached your existing customers is a good place to start. But also don't forget the power of word-of-mouth advertising. If your clients are happy with you, it's an easy thing to see if they know of any other small businesses that could benefit from your services. Once you have channels in use, evaluate the channels for cost/benefit effectiveness, but only once you have been using them.
As nice as it would be to have a system that 'guarantees' some kind of advertising success, don't fall for that. Start with the principles and just work at finding new clients.