Not much help, I know, but I've found my first interview (after a long period) to be dreadful, and I'm much better at the second. Probably just nerves. Go for a few interviews for jobs you don't really want, so when you get the one you do, you've got some experience under your belt.
What they are looking for depends upon the job. Make sure you know the job description by heart. Make sure you know your own CV as well. Think about how your work experience matches their requirements. They want someone who can do the job, be reliable and fit in with their other staff and company 'way of life'.
Expect something like "tell us about yourself" as an opener; this is your opportunity to sell yourself. There's often the classics like "tell us your 3 best qualities and your 3 worst". Or "tell us your biggest work triumph" or "...disaster".
I think its still true that basically, they've decided in the first 5 minutes, so first impressions make a big difference.
As an occasional interviewer, I looked for the things I described above and somebody who was relaxed about themself, if you know what I mean.