Employers frequently ignore the real value of a phone screen, as if the only point is to tell if the candidate is really a carpenter trying to get a job as a programmer before they are brought into a face to face meeting.
Yet the phone screen is really the first contact with a prospective contributor to the team or company not simply a filter. What you ask and how you handle it may get you a good employee or turn them away.
Of course there are people who are completely inappropriate to interview further. Some companies go even further and try to filter out people by requiring online tests or code challenges or even uploading something to Github. To me that way too much effort on both sides.
Every programmer has had many exposures to the phone screen and of course I have seen a ton of them over my 3 decades. What always struck me was how often the people doing them, who might be managers or just programmers stuck with the duty, treat them as a necessary evil to be dispensed with by asking rote questions in a bored voice. Since I am not a carpenter I often find the tone of a phone screen to be somewhat off-putting and possibly a turnoff on further contact. After all this is my first contact with a team or employer that I might spend months or years with. It's like meeting someone you might want to date and seeing spinach in their teeth and mismatched shoes.
One phone screen I had once started off with a question on "How do you define Objected-Oriented Programming?" and spiraled downhill into classroom questions and esoterica. Why would you waste 30 minutes asking student type questions to an experienced programmer? It's pointless and teaches you little and if you do this for every phone screen you won't ever get any real work done. If you do this for every phone screen no wonder you sound bored.
People often ask trite questions as well, as if the intent is to see if the candidate knows the difference between a class and an object which presumably a carpenter or dishwasher wouldn't know. But why persist with simplistic questions? It doesn't really teach you anything about them and if it's just a boring set of questions with no opportunity to interact the candidate also gets little sense of whether the team or company is worth continuing with.
What I prefer to do and would prefer to see is a variation of what I wrote about interviewing. The screeners rarely if ever even read the resume beyond the first job title, much less check out any links (my resume has this blog right at the top yet virtually no one ever mentions it). I think people assume all resumes are lies because some of them are. To me the resume is the key.
Pick a job entry, not necessarily the last one, and ask a few questions about the work: what did you do, how did you do it, what technologies and process, how was design and functionality decided on, what did customers say. Basically anything to see if they can detail the work. Anyone who did real work they put into their resume should be able to communicate in detail. I can talk people under the table about anything in my resume. Anyone who reads this blog knows all the stories I have.
If you worked on something every day for months but can't communicate anything about the work, you either never did any of it, you are a carpenter, or you can't communicate with programmers. All of this is easy to learn after only a few minutes. People can look up simplistic phone screen questions on the internet but they can't hide an inability to expand on what they actually did, especially if you ask questions about things not mentioned directly in the resume entry.
In this day of tweeting in chopped up sentences, real conversation not only provides a greater insight into someone's ability but allows communication to flow both ways. Instead of 30 minutes of pedantic carpenter questions you get a chance to get to know the person better so that when and if you bring them in you already have a reasonable introduction into who they are, what they can do, and how they will interact. The candidate also has a chance to learn and get some sense of how reasonable the environment might be.
So don't think of the phone screen simply an irritating filter chore but as a quick introduction to someone you might want to know more about. As a side effect you will also cut out the carpenters without it becoming a repetitive pain to do a phone screen. It's also a mini introduction to your company and your team and you shouldn't blow a chance at snagging a great employee.
If you do it right and make it a quick real conversation, it's not a burden on anyone. Candidates not qualified will stick out quickly and likely realize it's hopeless and good ones won't be disgusted with being treated like unqualified ones.
Real programmers should enjoy talking with real programmers. Besides writing code you spend a lot of time communicating in a job, so why not start up front?