Research. Know your subject, know what has already been said about them, what they've already said. Don’t be redundant.
Angle. Have a specific angle so that your story stands out and your interview has focus.
Observe. Whether it's a phone interview or in person. I think it adds such a layer to the interview or feature to be able to include those details that you observe about the person, like a study in a way. Anything from like what they're wearing, to what they were doing when they picked up your call. It adds another layer.
Let them speak. Don't cut them off! Sometimes you'll find it a little awkward if there's a small break of silence, but a lot of times I’ve found that it helps them answer better. They might give this short answer, but if you let them think, it's a much longer, more thorough and thoughtful response.
Everyone's a person. So depending on who it is and how hard it may be, just treat it as casually as you can. It makes for a more comfortable environment. I've always just preferred more of a conversational approach to interviews.
Draft up 10 questions. I don't follow a strict list; it’s more so to fall back on if the conversation isn't going anywhere. If it comes to a dead end that you have those to draw upon. So you never run dry.
Communication with the publicists is always key. That's pretty technical one. It's boring and sometimes it sucks, but it's definitely important so that you know what's going on with your subject. Especially if there are any timely projects that you can peg the piece to or any questions you need to ask, it's just really important strategically.
Edit, edit, edit. Especially with my conversational approach, interviews can always run really long, and even just as a consumer of media, especially right now with how short attention spans are, chances are no one's going to read the full thing. So sometimes it hurts, but I’ve cut many responses and questions from an interview just because it wasn't relevant to the topic at hand, or maybe it wasn't that interesting. There have been times where I thought it was maybe one of the most interesting parts of the conversation, but you know, you have to kind of think in the context of the piece and think about it from the perspective of the reader and sometimes it just doesn't make sense outside of that phone call or that in-person conversation.
Follow up. Don’t be scared to add a new question or ask them to elaborate on something they already answered.
Always made sure that your Voice Memos or recorder is working. I've had horror stories of like 30, 40 minute amazing interviews where I realized that I wasn’t recording. What a nightmare! But honestly, even then it's not the end of the world. It happens. There's not much you can do but contact the person, tell them what happened, and either suggest another phone call or just send them a list of questions and they'll respond with answers. It's not always as great, but it's a quick fix.