A process combining creativity, technical know-how, psychology and marketing savvy.  The web is let down when compared to more mature industries by the ease of entry into "Web design" and the lack of forced accreditations and compliance in its suppliers.  This is experienced at its worst at the small business end, where it is common enough to find people technically skilled in site creation (as the toolsets and template designs available now make entry to the market so easy) but who haven't the slightest notion of building a site to be marketable.  As a result 99% of the web is brochureware, perhaps attractive enough and useful enough in its own right, but destined never to be used because noone is ever going to find it.

You wouldn't drive your car to a garage where the mechanics approach you - hammer in hand to tap at things under the bonnet - before discussing your problems.  Yet small businesses take exactly this approach with their site design, either delegating the task to a "knowledgeable mate" or other scantly qualified new entrant to the business: banking too much on their own sense of creativity or competitor websites (mostly created under the same conditions) and too little on what the market is looking for.

There are 550 billion web pages out there.  Bank on the basis that your site will not be found, and if it is, that a surfer will have a choice of at least 30 other sites to go to if your site fails to make it clear what you offer and lead them to take action with you.  

This implies an up-front research process with your client to really get under the skin of their idea.  More times than not with a startup, this may be the first time the entrepreneur has had a hard, objective light shone on their "baby".  A good designer will not jup straight to look and feel, but to understanding the business - and with a small business client, very often it is the client who walks away with a better understanding of their baby than they had when they walked into the room.  This is just through process of forcing them to step through a typical business cycle, from initial customer engagement to sale.  Sometimes it also has to be said you may conclude there is no business underlying the enthusiasm and it is a test of your own scruples to come out and say so - or at least identify your key concerns.  DON'T just implement their ideas as-is and walk away with their money. It is far more valuable to both sides to create a relationship that will have legs, than perform a one-off piece of work that damages the reputation of both parties.  

So few small business designers do this and unfortunately too few entrepreneurs want to have the lid lifted off their idea to the extent that they need to.  Plopping straight into site design is so much more comfortable, but it really is not the correct starting point.