1. Timing. You need to know how long your interview is going to last. If your segment is 5 minutes then your answers need to be concise; if your segment is 12 minutes then you have a little more flexibility, but you should still not be giving 3-4 minute answers. You can easily say what you have to say in 60-120 seconds. Finally, yes and no answers do not make for good radio.
2. Passion. Are you passionate about your topic? You should be. You need to let your passion shine. Sounding monotone doesn’t tell people you are passionate, it almost sounds like you are sleeping. Be engaging, conversational and most importantly have fun with the host(s) who are interviewing you.
3. Informative. Lastly, you are being interviewed for a reason, you need to add value to the conversation. If you have pitched yourself for a radio interview then you need to come across as you know what you’re talking about, as well as adding to value to the listening audience.
Good luck! And please ask if you have questions.