Whether you're a blogger interviewing an author, or an author responding to a blogger's questions, it's very important that you both provide quality and professional work when it comes to interviews. I've been interviewing authors for over a year now, (and been interviewed as well) and I've noticed a few things that both help and harm the interaction. So I'm going to divide this up between Do's and Don'ts for both authors and bloggers.
Authors
Do
Provide all material requested from the blogger the first time around.
Edit your responses (spellcheck/use proper grammar and capitalization) so the blogger doesn't have to fix it.
Provide high-resolution pictures for yourself and your book covers.
Get your material to the blogger on time.
Answer all the questions (unless otherwise agreed upon) and provide interesting information. One-word responses won't engage the reader or the interviewer.
Post the interview around to your social media platforms and give the blogger credit.
Don't
Badger the blogger about when your interview is coming out or keep requesting changes (unless you have a book coming out and need to provide a sale link).
Act rudely towards the blogger. They're doing you a favor by creating the interview for you.
Answer questions dishonestly
Cut down other writers or bloggers in your answers.
Ghost the blogger.
Bloggers/Interviewers
Do
Get questions to the authors when promised.
Provide a designated day that you'll post the interview and stick to it.
Provide the author with a link to the posted interview so they can share it around.
Review the answers before you post it on your site in case of errors or controversial responses (depending on your site's dynamics).
Answer any questions the author might have about the interview or provide clarification.
Be honest to the author about what they can expect (are you posting the entire interview or just portions of it?)
Don't
Act rudely towards the author. You two are trying to work together to help one another.
Post the interview late or not at all.
Ignore the author's concerns if something is posted incorrectly in the interview.
Ghost the author.
Promise a posting date until after the author has provided their material. (I've missed posting interviews because authors didn't give me their information in time).
These are just a few ideas to keep in mind while interviewing and getting interviewed. Bloggers and authors should remember that they're working as a team. Together, they can provide exposure to each other. I've read far too often how authors have lashed out at book reviewers, bloggers, or interviewers for petty reasons. Bloggers can't post interviews without authors, but authors can't gain exposure without the help of bloggers. Work together harmoniously and you will both succeed.
If you both find that you're on completely different pages, then it's also okay to politely agree to go your separate ways. What it comes down to is respect. We're all professionals here, and it's important to treat each other like people and not invisible faces.