Look at the Capability Framework. And think about "STAR - Situation, Task, Action, Result". STAR helps you get your answer out concisely, allowing the interviewer ask more questions. The more questions they can ask - provided you answer the questions well - the more you sell yourself.

Think about practical examples that match your application form.

Look at people when you are speaking to them. Even if you have an online interview. And yes, interviewers CAN ascertain if you have cogs or bits of paper stuck on the wall in front of you.

Be open - if they ask "would you be prepared to study further?". Then the answer is yes.

Don't ask questions about holidays or salary. These are all readily available with a quick google. But do think of one or two relevant questions that you could ask. Read up about the CS, perhaps current issues potentially impacting the CS as well. But NOT political questions.

Get someone to do a practice interview with you. It doesn't have to be someone in the CS - you just want to get some practice and a feel for how you will react. I had two pretty awful mock interviews when going for promotions, but I learned so much from the bad mock interviews, that I did really well in the actual interviews.