Several stage performers use a pillow, put their face in it and scream in the pillow to release anxiety. Before an interview, visualise the pillow, and breath out hard as if you're silent screaming. Once the anxiety is gone, you can be natural and you'll be able to respond more naturally to difficult questions.
Also be honest, interviewers experienced in a certain field can very quickly detect of you're busy bullsh!ting them and once you do that, the interview is a lost cause. Rather be honest and say you haven't worked with something, but you have read a b c about it and would love to work with it rather than pretending you've worked with it.
Enthusiasm is important - if you're not excited about the company and what they do, they'll be less excited about you as well - that obviously means you have to read up on the company as well, understand their values, know about their products and have questions about all aspects of the company, not just about the role you're applying for.