After careful sorting the resume, I still had 20 candidates. 20 person from ~150 have passed the first selection that has allowed me to spend three-four hours for interviewing each of them. The main criteria of selection for me were:
- ability to training on a place
- skill to choose the optimum approach
- skill to gather and solve a problem in a non-standard situation
- a good knowledge base: that means, the candidate should know the history of computer technics, possess the theory at a high level, knowing not only "what to do", but also to know "why".
To know about their skill to gather and solve a problem in a non-standard situation, I was asked them, for example: "How to spoil a Windows-system, if you have physical access to the computer, but don't have any account passwords?" and, after that, I asked them about "How to patch spoiled system?". I gave some virus-action examples and asked, what they would do to prevent damage and return funcionality and the lost data with as little instrumets, as possible, and more questions on non-standard instruments usage. Once, I've asked a candidate: "Which question would you ask, if you were interviewing me, to know, how good I'm with non-standard situations?" :-)
To know, how good they are in finding optimal approach, I gave them a little practice in configuring web, or mail server, or network gateway for particular parameters ("I need it to be very fast web-server for small number of clients connected to it, and yes, I want some server-side scripting language on it, to show me some statistics, what should I choose and why do you thing that is better? Could you show me on our test-server, if you've got 20 minutes left?")
The ability to training on a place - not really easy to check, but I asked some of candidates to make sample configuration file, or a script, and then, gave them a little hint to see if they could do it better after that.
The knowlege base - one of my favorite parts:
What is OSI? Why TCP/IP called "protocol stack"? What computer science heroes do you know? What is Windows-registery? And what about Unix-like systems?
And very important thing - they MUST love their job! "Did you read some of the classic authors, such as K&R?", "How long you take a great interest in computer technics?", "With what you began to study computers?", "do you have test computers/little network at home?" (if it's true, that's a very good sign!).