In reply to Francisr5811:
Some (many!) years ago I posted this (which has been slightly edited) on the uk climbing newsgroup; it's still relevant in a general way, and I hope it helps.
There are a few issues here. Firstly, your own shoes will help. You get used to them, become accustomed to what they will and won't grip to, how you need to position your foot to get them to stick to things. They'll bend around the shape of your foot and develop a smell which may have the character of an independent lifeform but which is all your own work. Nice...
Secondly, ignore image, ignore what you've hired, ignore what your mates have bought. Fit is everything. Take your shoes off and look at your feet (you can do this now if you like, no-one's looking). What do you see? Are your feet long or short? Wide or narrow? High volume or low volume? How do you know? Do you spend a lot of time looking at other people's feet? The point here is that you *may* be making assumptions about the relative shape and size of your feet and you need to test those against reality - of course, a good shop will do this for you, but I don't know enough about shops in wherever it is that you live to recommend one to you. Which of your toes sticks out the furthest? This will dictate the general shape of the boot you buy - if it's your big toe, then you're after a boot that curves back, if it's your second toe then you want a boot shape that mirrors this. Which is the widest part of your foot? You want the shape of the boot to mirror this too.
Then, you need to ignore all the stuff you've heard about buying a half-size smaller, or that boots should be painful; it's rubbish. Get the ones that fit. One manufacturer's size x is not the same as another's; they can sometimes differ by a size (x=x+/-1), or even more. Don't get hung up about it. There shouldn't be excess space, the boots should bend in the right place (though different lacing patterns can tweak this, if it's wrong in the first place it'll never be right), they shouldn't slip on your feet and your heel shouldn't lift. You need to put the boots on and get yourself into a variety of strange postures to check this. Many places will have somewhere for you to try the boots out. If you can't, then you can often improvise (try standing like you would on climbing wall holds and see what if anything hurts).
And try your boots on in the afternoon, preferably the late afternoon. Your feet swell as the day progresses, so what feels merely snug in the morning might feel like chinese foot binding come the evening.
For all these reasons, go and buy your boots in person rather than by mail order.
T.