How would you prepare for a mid-level marketing interview?

By focussing on my past marketing experience, as because most of the questions will be related to it, and also showing my managerial capability.

Research the company, paying attention to news stories, their website and strategic plans. See if you can also speak to someone in your network that works or has worked there.

On the day of Interview, shine the shoes and plan grooming things like getting a haircut. Dressing well can increase your confidence as well as boosting your professional image.

You should know you CV and employers you have been working thoroughly.

Be prepared for tricky question apart from your Marketing Knowledge questions like: tell me about yourself?

Always start with a strong statement such as, I am a Marketing Manager with15 years' experience.  Then follow this with a summarized chronological story showing how you got to your current career position. 

 More questions such as, "where would you like to be in five years' time?" or "what are your weaknesses?" Why you leave the previous company? Be positive during such questions.

 Practice articulating each question and Writing down an answer is a good way to do this — reading it aloud, recording you or having a mock interview is even better.

At the end of the interview if Interview provides you an opportunity, ask a good question about the company not about the salary and benefits.

Always thanks the Interviewers to provide you an opportunity to be heard personally.

Research the company.
Tie in your experiences, education and practical knowledge to the requirements of the position.
Compose an answer regarding your strengths and weaknesses.
Make sure the weaknesses you choose are not really weaknesses...like perfectionist, workaholic and overly dedicated to team project completion.
Remember to expect and be prepared for the question...why should we hire you or how can you help our business.
Be creative and positive.
Have examples or back up stories.