Ask if you're allowed to take notes. If you are, do so. It can help you keep on track if you have multiple points that you want to talk about in response to a question. It also makes you appear thoughtful and diligent.

If you lose track of the question while you're answering it, ask for it to be repeated. This shows accountability and a level of respect for the interviewers. On a similar point, ask for clarification before answering a question if necessary.

Repeat the key parts of the question back as the opening for your response. This will help keep you on track and it shows that you are able to remember instructions and identify the important details, e.g. "So in a situation where I was experiencing conflict with a coworker I would..."

Take your time responding. Acknowledge the question but don't be afraid to take a few moments to start responding if you need to. This shows that you are conscientious, that you handle pressure well, and that you are less likely to make rash decisions that can cause additional work for management.

If a thought comes to you after a question has been asked and you've already moved on to another question, once you've finished responding to the current question it's okay to say something like "Regarding the previous question, I just wanted to add a little bit more to my response..." or something to that effect. This will convey that you are confident, that you are thoughtful, and that you are capable of asserting yourself when it's important.

If you are asked to come up with how you have handled a certain situation in the past but you do not have a decent example, say as much. "To be honest, I have only had minor conflicts with coworkers that have been resolved by discussing it with the person in question to clear up misunderstandings or with one coworker who just didn't like me so I kept out of their way because we didn't have much contact and there was nothing in their conduct which was over the line..." but proceed to answer how you would deal with a serious conflict: "... however if it was a major conflict that I was experiencing with a coworker, I would..."

If you are charismatic enough to pull it off, I find that being charming and disarmingly honest works well on the personal questions and when they ask you how you are, where I would say that I'm feeling a bit nervous but that I'm looking forward to learning more about the job. Something like that. But you have to say it in a way that isn't too self-deprecating or self-pitying and it might be culturally contextual so ymmv.

Also have two questions prepared to ask them at the end of the interview. It can be small, it can be big. Doesn't matter. If both of your questions get answered through the interview, be honest about it and say that you were planning it ask about x and y but they already answered those questions for you.

I would also recommend reading up on things like annual reports and similar official communications. Try to find the values and visions stuff. Pull out the key words they use to describe themselves as an organisation and try to reflect this wording in what you say, where possible.