How to hire a programmer when you have no technical knowledge?

With no technical knowledge, you shouldn't hire a programmer.

But the way you write about this, it's as if you are assuming you cannot gain technical knowledge. Unless you are a rock, this assumption is probably false.

So first step, learn about the domain of concern. Including some technical knowledge. You'll need at least enough to decide whether your plans are well considered, and to communicate your intent to whoever you might hire.

Then you could learn about hiring: http://lmgtfy.com/?q=should+I+hire+a+programmer

Damn, you beat me by a minute! ;)

http://lmgtfy.com/?q=recruitment%20agency

You might want to refine that search to include the area where you are looking to hire.

What if I want to recruit him on my own - I don't want to hire an agency to do the hiring for me. I need sb/sth to help me with evaluatuion of candidates.

It depends what you need them for, you're leaving out a lot of important details like task and budget. Contact me if you'd like to discuss, it's very likely I can help.