Speak slowly and leave pauses. You have to speak slowly enough for the journalist to keep up with what you are saying and leave some pauses so that the journalist has time to write what you have said. Watch what they are writing and don’t start on a new explanation if you see that they are still scribbling the last thing you said. One of the most common problems is to keep talking quickly without leaving any gaps so there just isn't time to keep up. Then it is hardly surprising if you are misquoted.
Always give answers that are complete. A good answer is one that is complete and will work without the question. This makes it much easier for people to quote you accurately. When the interviewer asks, for example, “What should you do to be quoted accurately?” a normal conversational answer might be something fairly unstructured like “Well, pauses. And slow down. Time to catch up, you know…”. This kind of response works fine in normal conversation but it is unusable in an interview. A much better response would be something like “If you want to be quoted accurately in an interview you should speak not too quickly and leave some pauses when you see the journalist is busy writing.”
Think before you answer. Don’t rush to answer before the question is finished. Take your time, think first and then state your points as coherent thoughts without rambling. If you find yourself rambling consider restarting the answer. If you give a very messy answer it will need to be reworked more and this process can introduce changes in emphasis that you would call mistakes.
Talk in a normal conversational tone. Speak in a normal conversational voice and avoid sounding like advertising copy or a bad press release. When your answer sounds like advertising it can't be used without some twisting so it is very likely to be ignored or distorted. So, for example, if someone asks "Why has acme.com become so successful?" never answer with something like "World leader in enterprise grade acme's, Acme.com has been voted the world's most voted acme provider for three consecutive years and...". Just answer the question. You're not writing a press release.
Spell out acronyms, names and other unusual terms. If deadlines permit consider sending an email with the names and technical terms spelled out but ask the journalist first. And be especially careful when you are using a common acronym in an unusual way. To most people B2B means business-to-business though some people now use it to describe brain-to-brain communication. Spell out your own name very carefully and give the journalist a card to help them get your name right. This is not just about your pride; it is also important so people can find the interview with search engines.