Make sure you have real expertise in your topic area (or, if you're interviewing somebody else, make sure they are an expert). This means you will sound confident, the recording will flow easily, and you won't have to keep doing re-takes because of mistakes.
Choose the best environment for the recording:
- Choose a quiet time, and one when there will be less chance of interruption.
- Tell other people you're recording at this time, so they don't interrupt you.
- Turn off your mobile phone, and take other phones off the hook.
- If using your computer for recording, shut down all programs that might chime in with alerts or messages.
- Have your notes and any other resources organized and close to hand (to avoid rustling papers, moving things around on your desk, and so on).
- Keep a glass of water at hand.
Whether you're recording in person, over the phone or by Skype, investing in a relatively good quality microphone is important. You can get fairly inexpensive high-quality microphones which can make a difference to your recordings. However you may need to experiment with a number of different microphones to get the best one for you.
Recording directly to your phone (e.g. iPhone) is very convenient because you can do it at any time and anywhere. Although you can speak directly into your phone, you can get better quality by using a microphone.
If you're using Skype for your conversation, close other software on your computer during the recording, especially software that's using the Internet. You will also need to invest in recording software (there are a number of free and low-cost recording plug-ins available for Skype).
Enunciation is about speaking clearly, and in a way your listeners understand easily. Speak clearly (but not too slowly), and be aware of any poor speaking habits you know you have (such as "droppin'" the ends of words), so you can take more care with them in the recording.
In an interview, there's not much you can do to improve your guest's enunciation. But if you think something won't be clear to the listener, politely repeat it to the guest in the form of a question (For example, "When you said 'greater economic freedom', were you referring to personal or corporate freedom?").
If you're doing a solo recording, it's easy to fall into the trap of speaking without expression because there isn't anybody else present. To avoid this, imagine speaking to somebody else, and use all the expression (and even gestures) you would use in this situation.
Even in an interview, some guests become wooden and boring when they know they are being recorded. As the interviewer, it's your job to put them at ease before you start the recording, so the interview sounds interesting and dynamic.
Finally, there's no substitute for experience. The more you do this, the more comfortable you will become at it. So don't hold back just because you think you're not good enough yet!