Yep, research is your best ammo but make sure you hold something back; even if you know the company makes 100000 pounds on plastic dogs or whatever make sure you ask an interesting and related question to show how you want to learn etc.
Try researching the person interviewing you if possible; that's always great ammo.
Wear clothes that are appropriate and you feel comfortable and confident it; I imagine that'd be a suit in your case.
If they offer you anything, go for it. I normally ask for some water. That way you have something to "play" with if you need a second to compose yourself.
Get the location and if it's close enough do a dry run for timescales etc, if not then leave plenty of time and scout it. Don't turn up too early - 10 mins at most.
Then afterwards later that day send a nice email to say thanks for taking the time to interview me and show your continued interest in the position.
That's all off the top of my head!