Although I have had a number of experience doing user centered design sessions or design sprints…actually conducting the interviews and research of usability testing was fairly new to me. Just like anything new the only way to get better at something is to practice, practice, practice… and do research to become a student of the craft you want to become better at. It also helps to be involved in UX and the entire process so that you know what to look for, what to ask for, how to understand what you do in usability testing will translate into actionable items.
A good resource article that I ran across was Honing Your Usability Testing Skills: An Interview with Ginny Redish and I really like these simple bullet points here from this article:
Some aspects that I find design teams often need help with are:
• Thinking about the issues—what you want to learn from the usability test
• Writing good scenarios—that test the web site or product without giving away too much
• Facilitating comfortably—knowing when to talk and when not to, how to ask neutral questions, how to keep participants thinking aloud
• Taking good notes without missing anything critical
• How to report results so that the right people act on them