Having interviewed and hired lots of people of the past few years, I know how hard this can be. I've made a few mistakes, but also got some really good people. One thing I often try is to get the candidate to describe key aspects of a system he or she has worked on. I always have a blank whiteboard, and a bunch of pens visible - but otherwise I don't draw attention to it. As the person describes key components and how they fit into the system, the good ones invariably ask to use the WB to help explain. Now, I'm not after UML here, but simply the ability for a candidate to explain how things he has worked on fit into the bigger picture, what the key processes are, and - if they are on a roll - where the problem areas are. Personally I don't put too much emphasis on code tests - most of the ones I come across tend to be done by current employees trying to show how smart they are, as opposed to be being designed to test whether someone has the knowledge required to be successful in the role. The ones that do have value are those that allow the candidate to explain their answers, and also perhaps to ask for clarification on the questions. This can get into an interesting technical discussion often miles away from the narrow confines of the original question. A lot of hiring is gut-feeling. But you can protect yourself to a certain extent by having a probationary period in the contract. This will only work well, however, if you really think through what tasks the candidate will do during this period, and how success can be measured. Simply adding them to a team and hoping their work will be OK can lead to the probationary period being taken up with trivial easy tasks that still leave you non the wiser on their real potential by the time you have to make a decision. This is a particular trap I fell into once, and I ended up keeping a guy on I should really should have kicked when the contact made it easier. This is in the UK, btw, where employment laws on hiring and firing people are probably tighter than in the US - but at least it's not France!