Can you code?
This is, apparently, and important questions you are to ask any potential software developer you are interviewing. Surely this does sound unreasonable, yet you will be surprised with the effect this question and a minor task to test such abilities causes on potential employees.
Incredibly many people attending such interviews have absolutely zero (meaning none at all) experience nor skill in writing code. Surely this may be caused due your job offer being their firs employment opportunity and you are also realizing everybody needs to start from somewhere and you are looking for a junior specialist (maybe) but, there have to be at least some basics a candidate is capable of, right?
Now that you are aware of potential dangers a huge amount of candidates are hiding (even certificated specialists who have been through years of college) you may come up with a solution that is smooth and easy.
While interviewing a person come up with a simple test task that is not too hard and you will be astonished. Something as easy as a program that should do something as, let’s say print out numbers from 1 to 100 replacing all numbers that are even with any word or sign of your preference. The task will not be taking more than 10-15 minutes from a skilled programmer. The astonishing thing will be that 90% of your interviewees will fail despite all their comp sci graduation certifications and imaginary years of experience.
It would be even preferable to make candidates complete such tasks before the actual interview to save time. It may be something as easy as writing a loop from one to ten in every language from their resume. You will have much less candidates and you will not be spending any time on unskilled developers. Pure profit.