While a technical phone interview is not very different from the other interviews, it does require a different type of presentation. Here, what you speak is just as important as how you speak. In most cases the interviewer will be far more interested in your ability to solve a technical problem or to talk about the latest software release than anything else.

No preparation:
One of the biggest mistakes that interviewees make is not preparing themselves well enough on the technical subjects they claim they are good at in their resume. More often than not, they think that they will be able to work around the questions. They think that by giving creative but vague answers they will be able to fool the interviewer into believing that they actually know a lot about the topic in question. This is such a poor trick that I have seen interviewers cut off several candidates trying to do this from their list instantly.

Lying about technical knowledge:
In most cases, the interviewers for technical interview will be a technical person himself and will be able to catch any lies immediately. Trying to fib is far worse than being honest and if you do not know the answer to a question, it is safer to say so rather than twist it around with your creative words. In technical phone interviews, the questions are very direct and there is little scope to make up a new answer. You either know about a technology or you don’t.

There are many who will make their resume impressive by mentioning some really advance technologies and then fail to answer a simple question on OOP. In fact the interviewers will even be able to tell if you have worked on a technology or just have some theoretical knowledge. So, under no circumstances should you make lies in interviews.

Trying to cheat:
Most of the interviewees rejoice at the thought of technical phone interviews because they think that they will be able to cheat. They imagine that they will be able to refer to all the books and websites while answering the questions. Naturally, this is possible because the interviewer cannot see you.

But if you think that just because the interviewer is not in front of you, he will not be able to know if you are referring to other sources, you are completely wrong. Since you will not know the questions you may be asked during the interview, you cannot open the correct websites and bookmark the right pages beforehand. This means, that you will have to flip through the book and type in the name of websites to be able to find the answers to the questions. This will take you long enough for the interviewer to know what you are up to. It is better to avoid the temptation to find the right material during the interview process. The image you present, in such cases, is always a poor one.

However, you may prepare a simple cheat sheet to remind you of some key points but at no time in the phone interview should you let the interviewer hear typing sounds or sounds of flipping pages. 

Exaggeration of skills:
Another pattern followed by interviewees in interviews is to exaggerate about the number of software packages they have worked on. For instance, if you claim that your previous project involved creating database tables in Oracle and you fail to answer a question like “what are the different normalization techniques in SQL?”, you will be inviting trouble.
Thus, be honest and mention only those technologies in your resume which you actually know. Due to the extremely fast developing world of software technology, many IT professionals fear that they will not get the job if they do not claim to know every single new language. Trust me, while most employers would love it if you did know something about the newer software, no interviewer is so silly as to expect you to be a master in every new technology that floods the market. As long as you answer the questions on the technology that the company wants you to work upon, you will have excellent chances of getting hired.

In fact, at times, for fresher, companies do not even expect perfect knowledge on any technology. If as a fresher, you are able to demonstrate a basic understanding of programming and software principles, you will be considered a strong candidate. This is because, most IT firms give training to any fresher after hiring him and if you show an eagerness to learn and knowledge of software systems, the employers will consider you fit for their training on specialized software.

Other common mistakes to avoid

Lack of enthusiasm:
A mistake frequently committed by interviewees is that they do not show enough enthusiasm for the job. You should show that you are excited about getting this job. This will impress the interviewers and make them believe that you want the job as much as they want you.

Not verbalizing your answer:
It is a huge deal in technical phone interviews as the verbal communication is your only tool. I always recommended that you explain your thought process to the interviewer. More than the right answer, the interviewee is looking forward to monitoring your logical thinking ability. Many interviewees sit quietly if they feel that they are not getting near the answer or they just mention the answer without explaining the process by which they reached that conclusion. To really win some extra points, explain clearly, how you proceeded with the problem.

If English is not your first language know how to pronounce not only abbreviations but also all the special symbols and characters i.e.  @ - ‘at’, C# -“C sharp”, “# - pound sign”, “{}” – parenthesis, “()” round brackets, “-“– dash, etc. 

This would be very helpful in answering language specific questions like:

“How do you declare a two-dimensional array that you don’t know the dimensions of?”  Answer:  int[,] arrayName;

or

"How do you initiate a string without escaping each backslash?"  Answer: Put an ‘at’ sign in front of the double-quoted string

Your main goal on the technical phone screen is to show that you have required knowledge and experience and that you are worth being allowed into the technical interview in person.

Getting intimidated:
Getting fazed by the interviewer is another issue with the interviewees. You do not have to be scared! The interviewer may sound intimidating because of the hot seat you are occupying but you should always believe that you can do your best. The interviewer is only another person trying to understand if you are good enough to be his colleague. If you think positively, understand the interview pattern and come prepared with your subjects, you will not be afraid of the interview or the interviewer.

Not taking cues from the interviewer:
How you behave in the interview will depend a lot on the mood created by the interviewer. If he seems chatty and humorous, you can try to be informal too. At no circumstances should you lower your guard enough to pass some off color remarks or jokes. No matter how friendly an interviewer acts, he is responsible for hiring you and any mistakes on your part may always rub him the wrong way. If the members of the interview sound solemn, you should be serious too. In a nutshell, take cues from the interviewers themselves about your approach to the interview.

Of course, it gets much more difficult to understand the attitude of the recruiter or the interview pattern he is following without seeing him in person. This is one of the biggest issues in technical phone interview. Since, you cannot see him you cannot understand his body language or take cues from his facial expressions. This makes it all the more necessary for you to be on your guard always. 

Being not confident:
To be able to answer the interviewer’s question confidently, you need to be confident. You have to start the interview with the belief that this job is for you and if you do not get it there is a better one waiting for you somewhere. A healthy and positive mind set can go a long way in making you look confident and professional. Another point that you must remember before taking on any question is that you completely understand the query itself. In case you feel you have missed a line or have not grasped the intent of the question, you should not hesitate in asking the interviewer to repeat it. The interviewer will be happier to oblige you with a repeat of the question instead of hearing you give an answer that is completely off the mark.