Its easy to determine experience. Its right there on the candidates resume. You can also do reference checks and speak with past managers to get learn more about a candidates experience. But intelligence is not as straight forward. So how can you determine a candidates intelligence?
One way is testing. There are plenty of online IQ or logic tests that will help to figure out a candidates intelligence. Testing is not the “end-all” tool, but it can be part of an approach.
Another way, and perhaps the best, is by paying more attention to the questions the candidate asks rather then the answers they give. This will give you insight into the way the candidates mind works. How they view the world. Do they view the job as a mindless 9-5 position or do they understand the greater impact of what they will be doing? Its not about the questions the candidate answers, its about the questions they ask.
To increase your chances of hiring IT workers that will have a positive impact on your company, always err on the side of intelligence over experience. You will be happy that you did.