Tie it back, wear a suit and arrive 10 mins early carrying a broadsheet newspaper you can read whilst waiting (financial times is too obvious though unless the job involves finance).
All good advice! Although I once had an interview from hell in which none of that did me any good. (my hair is down to my arse by the way)
The first 10-15 minutes went brilliantly, but then the interviewer sat back and said:
"You seem a nice bloke and you've impressed me so far, but what I don't understand is why you've come in here wearing a suit and tie yet you also have long hair."
I responded with the obvious point that quite clearly no candidate in their right mind would turn up for such an interview in anything less than a suit and that I doubted I'd have gotten this far into the interview wearing jeans and a t-shirt. But that wasn't good enough, as his response was simply:
"All good and well, but that's not really you. I'll bet you don't wear a suit at home. Infact, what do you do in your spare time. Do you drink? Do you smoke? Do you live the rock and roll lifestyle? Our customers are very respectable, I wouldn't be happy with you representing our company."
I countered it all very respectably and took it very well in my opinion, but I have scarcely come accross such a complete cockstain in my entire life! As has been said previously, if that's the attitude of an organisation, why would you want to work there in the first place?