Interviewing for a job is hard because you have to bring so many skills (marketing, sales, communication, negotiation and presence) together to do a good job. If you have not practiced well, you will make simple mistakes that could easily be avoided with some practice.
You can make incremental improvement by not just practicing, but by practicing in a deliberate manner. This means you have to know what you are doing wrong, can get feedback from others to help you improve. This is hard work since it is very hard to break bad habits, especially when you can't even see it yourself. As the great golfer Ben Hogan used to say when people asked him about the secrets to golf. He would say that "It's all in the dirt." In your case it will be all in the audio and video.
You have to focus on how you come across on the phone, in a face to face interview and handling objections.
For phone conversation, all you need to do is record your voice and listen to it.
Do you like it? .
I am amazed that so few people ever listen to what they sound like and then make some quick fixes such as slowing down the pace, calibrating their timing, pitch, emphasis, etc. You can practice this anywhere and at anytime. You can even do this while you are diving. In fact, I do this when I go for a long walk (more than 30 minutes).
For the face to face interview, I recommend you do a video recording since you need to see a video of youself answer both basic questions and difficult ones. Note, communication is not just what you say, but how you say it.
Lastly, you also want to focus on objections since every one of them could be a potential showstopper. The interesting thing about objections is that often how you handle them can mitigate or even remove any doubt the interviewer may have about your potential fit.
The way Nixon changed the whole narrative was just masterful. During most of the speech he was explaining about some illegal funds that were made to him, but as he got closer to the end he got very personal. He brought his wife (Pat) into the speech by saying she did not own a mink coat; she proudly owned a Republican cotton coat. But he was not done. He then brought his two daughters and the dog (Checkers) they had received as a gift. And he was emphatic that--- no matter what --- the family was not going to give Checkers back. This made him look like a victim and viewers (the largest at that time) overwhelmingly supported him and thus was kept on the ticket by Eisenhower as Nixon went on to be the Vice President for two terms.
To get good at interviewing, you have to treat it as a skill that you want to improve. I like the four suggestions offered by Sims Wieth in the blog "4 Short Lessons on How to Learn a New Skill" in Inc. related to public speaking that you can apply for improving your interviewing skills.
You need motivation
You have to make a commitment to make a change; the hardest thing to do is to get started. I know there is no shortcut to learning than by knowing first, then doing second, and analyzing third You don't want to blow an interview when you can prevent it by making some simple changes. You should not wing it. If you succeeded in the past then you probably got lucky (or are naturally gifted). The past success is not always a good predictor for future success as the common disclaimer you see when it comes to investments. You definitely want to be confident, but not arrogant that you don't practice.
You need knowledge about how to improve
Just by interviewing more will not make you improve. You may be perfecting your bad techniques. To get better, you need to first know what works and then what you need to do to improve. Motivation has to be met with knowledge, practice and feedback.
To do well in an interview, you need to do this under pressure. See if you can get someone to get another person you don't know do a mock interview and video tape it. You can then analyze it and see how you came across. It is ok to give the questions in advance. Once you have the video recorded, get others to evaluate your performance. This is work, but it is worth it since it can save you plenty of time and headache; also it will give you more confidence when you are going for a real interview.
You need the ability to evaluate the outcome.
You will not be able to figure it out. If you can find a good interview coach, you want to work with him so he can point out some things you can work on. The coach has to be very specific and make you see the before and after video so you can see for yourself the improvement you are making based on coach's recommendations. If you can't find a good coach or afford a good coach, try to see if you can get someone on the Internet do it for you for a fee. Whomever you work with as a coach should not be someone you know otherwise you may not get an objective feedback that you need to improve.
Ramit Sethi talks about a similar approach on "Ask Altucher" podcast on how he was able to secure scholarships when he was in school. When applying for scholarship because he could get interviews because he could write well, but was not winning the scholarships because he was not acing the interviews. Not until he had people video tape him did he see what he was doing wrong such as looking awkward, not smiling. He analyzed the video to see what mistakes he was making and broke it down till he had it fixed such as smiling does make a difference. This did require making a change of not doing the same thing and expecting the same results. He says that people "would rather do the same thing and fail then try something new and potentially fail." Once he made the changes through hard work, he was successful in earning over $200,000 in scholarships that paid for his undergraduate and graduate education at Stanford University.
When it comes to interviewing, you need to practice hard from the first call you will receive to the last call you will have. You can't leave anything to chance. To do well, you have to go from an amateur mindset to a professional mindset. The hallmark of a professional in any field is that he does many small things real well that shows up in the results.
If you don't have much time, the least you can do is to record your voice on an audio recorder, smartphone or computer and also record a video. This does not take more than couple of hours, but it will payoff in a big way. Just like anything that you need to be good at, you can only achieve it though deliberate practice. Interviews are too important to leave it to luck alone.