I do quite a few interviews for developers, business analysts, testers, and the like and you'd be suprised at just how poor some of the applicants can be.
You get these resumes with all sorts of wonderful references, great job history, experience on all sorts of cool projects and then they turn up and you just can't quite figure out how the resume matches up to the space alien sitting in front of you.
Here's an example:
I have a standard interview question that goes something like this: "We all have times in our life when we could have shown better judgement. Can you tell me about a time when you could have shown better judgement?".
Now most people ask wether they should answer with something work related or something personal (to which I say either) and then give some example that's not too embarassing for them.
However in this case, the applicant looks at me and with a dead straight face answers "The day I asked my wife to marry me.". I immediately burst out laughing, and only when the guy looked at me uncomprehendingly did I realise that he either competely misunderstood the question or he was serious.
Needless to say he didn't get the job.
Oh, by the way, we had an applicant visit the offices today. They were an hour early and were asking for a someone who never worked with us. After a few questions they realised that they were not only far too early, but that they were also on the wrong floor of the wrong buulding. I guess the company logo in the reception area was mistaken for a piece of abstract art or something.
So for some general interview tips - remember where you're interview is, and listen to the questions :-) It makes life amusing/furstrating for the interviewer when you get it wrong, but I don't think that should be the objective - do you?