Hi,
Well if it hasn't changed since I went for my first viewing nearly a year ago then you're given a time to turn up. Bear in mind there could be a lot of people given the same appointment. They have a list of everyone who's attending that time slot and I know I was top of the list but I have no idea how I got there. Plus I didn't realise until after I'd looked at only a couple of apartments and I had to go back around again to make sure I wasn't missing out on a perfect one.
My advice is when you get there ask where you are on the list; take a good look at everything on offer and after that if you have your heart set on one in particular keep your fingers crossed that no one else ahead you on the list chooses that one.
You'll also have to have you 3k deposit there and then too I think, and you might have to have your solicitors details too.
Best of luck
FTB1975