These are the mistakes I see beginners make repeatedly. The good news is, as long as you're aware, you can easily fix them.

TIME MANAGEMENT

Context setting and problem definition should take less than half of the interview time, so make sure you leave time to show your interaction design skills.

OVERKILLING IT WITH CONTEXT

As a product designer, it is important that you have a strong understanding of the context before solving a problem. But you can also go overboard with this and run out of time, resulting in a superficial pass at solutions.

JUMPING INTO SOLUTIONS TOO SOON

The flip side of this is understanding too little context, which leads to lack of solid problem definition. This results in the solutions made on the basis of shaky logic.

FOCUSING ON UI DETAILS

Unless your interviewer specified about wanting to see UI details, focus on interaction flows. Showcase how you define problems and determine solutions, instead of your ability to make components.

NOT VOCALIZING YOUR THOUGHTS

The clearer you can verbally communicate what you’re doing, the easier it is for the interviewer to understand your process and provide feedback. The balance of speaking, doing, and engaging is  best achieved through practice.

NOT ADDRESSING INTERVIEWER FEEDBACK

Interviewers will observe how you respond to their input. How you adapt or brush off feedback will signal to the interviewer what it’s like to work with you.

DIFFUSED FOCUS

Pick one big problem that you can solve well in the allotted time. It’s tempting to fight on multiple fronts, but you won’t have the time for that here. Choose meaningful focus over diffused diligence.

GET DEFENSIVE

No interview challenge is perfect, especially with such a limited time to assess your skills. However, it’s unproductive to use the time to refute and question the validity of this challenge. This is considered unprofessional and may cost you the job.