I recommend clarifying the structure of the phone interview with HR. Depending on the office you will have a regular case with an HR or just the fit part, so the preparation is the same. It will be interviewer-led. Standard parts - Structure, calculations, creativity, recommendations.
Don't worry too much about the HR - they are trained to do that.
In some countries they will also ask the simple personal questions:
- A story about yourself (walk them through your resume)
- Why Consulting
- Why McKinsey
After the case, you'll have a chance to ask your questions to the interviewer. It's important to prepare them in advance.