Hi, Great question to post. I've been in your situation a number of times so understand where you are coming from. Both from startup's i've had through to working on Go To Market strategies in large businesses.
The first place i would look to is defining geographically where i wish to cover e.g a local area or national or do i wish to span several countries?
Next, look at the new business "birth" rate and "death" rate within that region. This will give you an idea of a high level gross add's and net businesses you could work with assuming you wish to be helping them in their "early life startup phase".
Depending on how specific your new product is, you should look to segment further. However I am a big fan of looking at my customers or potential customers based on how they behave and "Buy" - too often we get focused on how to "sell" to new customers but not understand the former.
Also, think about this. Are they motivated to participate in your coaching program, or are you looking for people that require motivation to make their business successful, in turn they are looking for coaching? Again this will then help you to further drill down into "who" the clients are and "Why" they buy. It will also define where you should be networking etc or finding new business.
Happy to talk further over Skype or Google Hangouts if you wish to. I'm based in New Zealand, currently working for a global SaaS provider. NZ is +12 GMT.