Prep your answers
You can't always know exactly what questions will be asked in an interview, but you can still practice the answers for the questions you anticipate. Often you only need 5 - 6 answers ready, because you can use them to answer more than one question by changing them slightly. For each interview, look at the job posting and read about the requirements. Think about other interviews you had for similar jobs, and what questions you were asked. You can anticipate what you may need to answer based on what the company is saying about the position. You can also often find common interview questions for different professions by doing an online search.
Have a structure for your answer.
No matter the question, a good answer will always have a clear structure. Use a topic sentence, then give supporting details, and finish with a summary statement. Include language from the question in your answer to make sure it is clear to the interviewer that you are answering what they asked, and to keep yourself on topic.
For example, if the question is "Tell us why you are qualified for this position?", your answer should have a structure like this:
I am qualified for this position because of my previous job experience, education and special skills.
In my previous position as ___, I was responsible for ___ (list responsibilities which are included in the job you are seeking).
I have a __ degree in ___ (or state other relevant education).
I also have expertise in ___ (list other skills you have which line up with the job description/requirements).
In summary, my previous work, education and skill set make me a highly qualified candidate for this position.
A good way to try this is to write your answers out so you have a plan for the structure. You won't say it the exact same way when speaking, but it can be easier to organize our thoughts in writing, which will help us when it comes time for speaking.
Actually practice saying your answers out loud.
Just thinking about your answers is not enough - actually practice saying the answer out loud. When you do this, you'll find the potential pitfalls that you want to avoid during the interview and have a better chance of giving the best answer possible in the actual interview. You don't need to memorize an answer or say it the exact same way, but if you've said the answer several times while practicing, you'll feel more confident and prepared when it comes time to do in the real context.
Use strategies For Clear Communication
One of the errors that we make in interviews is rushing into our response, or feeling like we have to talk continuously without pausing. Often, a shorter, more thought-out answer is better, and using some pausing can help your listener have time to think, to understand your speech better, and to make notes on what you've said.
When you first hear the question, you can say a phrase like "that's an excellent question," or "yes, that's a good question, let me think about that a moment," followed by a pause. This acknowledges the question but gives you a moment to think about which of your prepped answers fits best, the structure of your answer, or what to say if you haven't prepared an answer that fits. Another good strategy to give yourself time to think is to repeat or rephrase the question. This also ensures that you understood exactly what was being asked and don't accidentally give an answer which doesn't match the question. For example, you can say "Let me make sure I understand your question. You're asking what experience I have with ___" or "Good question, so you'd like me to talk about a time when ___"
While you are giving your answer, make sure to pause between phrases and sentences. It may feel to you like the silence is too long or uncomfortable, but using short pauses actually makes you a more interesting and engaging speaker. It allows your listener to process what you've said, and it allows you to breathe, think about your next idea, and stay on track with your structure for your answer.
Mirror the interviewer.
Another good communication strategy is to reflect back to the interviewer. You can do this by repeating and rephrasing their questions (strategy detailed above), and by using similar words and phrases. If you notice that the questions use specific terminology, make sure you are expressing your ideas with the same words. Not only does this make the interviewer feel confident that you understood the questions, it also makes them understand your answers and relate to you better.
You can also reflect back to the interviewer in your body language. When you use similar body positions and gestures to the other person, it puts them more at ease and makes them feel a connection to you. (Read more tips about body language here.)
Plan for pronunciation.
While you can't really focus on accent and pronunciation during an interview, you can plan ahead a little bit to avoid issues that may arise due to challenging words and accent error patterns. Following the steps above will help you be prepared and confident. When you practice answering questions aloud, notice if there are words you struggle with. Is there a different word you can use which you feel more confident saying? Does slowing down slightly on the word help? If you know for sure that you will need to say a challenging word in the interview, practice repeating that word by itself, and then in short phrases, so that you don't have to focus on it in the interview.
For example, if I find the word "rural" hard to say, but my last position was in outreach to rural communities, I can practice the word by itself, then in short phrases like "rural communities, rural outreach, with rural populations, rural groups" etc.