I echo lfb's post!
The STAR system really does work well, it also gives you the ability to bring yourself back if you find your rambling on a bit, just think which bit you should be on and go from there!
As for shaking hands, won't do any harm will it!, if your offered a drink take it, even if you don't drink it you can use it as a pause while you collect your thoughts if you need to!
Do you know what PQA's you will be questioned on?
Have a look at the brigades website for ideas on questions to ask, in my interview (last November) I asked about a scheme they are running for children and how I could get involved as a probationary Firefighter, anything to do with Community Fire Safety is always a good one!
Good luck, the interviewers aren't there to catch you out but to get as much information about you as possible in the relatively short time available, and sometimes people do actually pass, I start my recruits course on Monday!!