Here are the most common app critique mistakes I see being made.

EXPLAINING WITHOUT CRITICAL ANALYSIS
Interviews want to know your product and design thinking, not an explainer on how it works. 

GOING Q&A
Be prepared to lead the flow of the conversation. You're ready to give your interviewer options instead of expecting them to provide direction and know all the questions.

ALL PRAISE, NO SUBSTANCE
I’ve encountered situations where instead of critiquing, the designer lavishes praise on a popular app. This indicates to the interviewer that you aren’t lack the experience to think critically on the work and you assume that whatever’s been launched is best.

FOCUSING ONLY ON UI DETAILS
Avoid pointing out all the things that look off on the UI. More often than not, it’s obvious to your interviewer.

LACK OF STRUCTUREThough this is an improvised performance, you want to set guidelines for this session before you dive in and go deep in your assessments.