They don't have to be technical overall, they need to be domain intelligent and product/capability informed. Finding the holy grail of sales person that is solid technically and solid in sales is tough and expensive.

My 2 cents: First, incentivize current clients for referrals. Referrals can be critical. Second, find someone who can do lead generation for you, and than parse your week into following up on leads and moving current projects forward. Once you are too busy to do both, than hire for whichever side you can find the best suited person. e.g. programmer or lead nurturer. Lead nurturing usually takes a little time to turn into a paying project depending on the size, so usually you can find sales (or even interns etc) people that can fill that role that aren't technical.

I don't think there is one correct way, but there are a number of known and different patterns that have been used successfully. The key thing is to avoid the common feast/famine mode and to get a solid and steady project flow. That only happens when you have leads and time to nurture them to into sales.