You need to start by looking at the points you made about your skills and experience during the first interview and try to identify what impressed them, and what they were less impressed by. In that way, you can give them more of the aspects of you that went down well and counter questions you felt you struggled with before.
If they’ve told you who the other interviewers are, there would be no harm in doing some research to find out how long they’ve been with the company, what they’ve done and what companies they worked for before.
Second interviews are usually a bit more intense. There might be senior people present at the interview to ask you about your specialist skills. If that’s the case, be confident in talking about relevant parts of your background. Have a few examples ready to illustrate them all so that you can be more specific about your answers.
Some interviewers ask them, others don’t. But you’d do well to be prepared for questions that apparently come from nowhere, as the panel may just want to see how you deal with it.
Don’t forget to ask your own questions
Second interviews are a better time to ask lots of questions as you can make them more relevant. Always ask hiring managers what they like about the company, what they think its goals are and how well it achieves them.
The second interview can often include meeting a few other people in your potential department or taking a short tour. The main reason for this is to make sure you're going to fit in. If you are a good fit, show it; but if you aren't, you probably wouldn't be happy working there, anyway. This is your chance to work out if you’d get on with your future team mates too and if you’d accept an offer.
Taking the offer
If they don’t make you an offer straight away, ask about the next step and how soon they might be able to give you a decision. But if they do, no matter how much you want to say yes, say thanks instead and ask for some time to consider. There’s no point spending the next few months of your life in a role that isn’t right for you, so you need to think about it.
Don’t forget that all-important thank you note. Even if you don’t take this particular job, you’ve made new contacts who might remember you when they move on. And networking is valuable.