having worked as a bootfitter selling "custom" fit boots to first time buyers, i have much experience with the points made here by steve turner.
when i fit boots, i pull out a brannock and re-measure the person's foot. i do not listen to ANYTHING the customer tells me. yes, this is disrespectful, but it's necessary. most consumers haven't the first clue about what a ski boot should feel like. i don't even use the brannock to measure the person's overall foot length, rather i use it exclusively to measure the bone structure length of the foot and the width. it also gives me an opportunity to view the overall shape of the foot and learn the instep height relative to the foot.
before i even pull out a boot, i describe the characteristics of the consumer's foot to them. i then explain what they are looking for a in a good boot fit, mainly the importance of a snug fit across the forefoot from the sixth toe to the ball of the foot, so that the foot CANNOT slide side to side in the boot. i explain the importance of being very aware of the boot on each side, without pressure points building, of course. this discussion also includes pointing out how it is just fine, even advantageous, to have the toe box of the boot open up to allow toes to relax and spread out - for better balance and feedback. the other important factor is the instep height and length. if the consumer's instep is evaluated and the proper fit is attained, the boot WILL NOT ALLOW the foot to slide foreward in the boot because the boot's instep height is holding the foot back in the boot. people who buy boots too big end up with smashed toes, because their toes can slam into the front of the boot when the foot slides foreward. if the foot cannot slide foreward, toes generally to never get smashed. once i have explained all this, the consumer is now expecting a certain "experience" when they put a boot on their foot.
i then pull boots in sizes that i believe are appropriate, based on the bone structure length of the foot, not the overall length. then i shell fit. i never tell people the size i am working with, because the preconceived notion they might have about owning a size 8 boot as a grown male can be ridiculously inhibitive to a good boot fit(you know what what's true about people with big feet? big socks). when i feel i have a good shell fit, i put the liner back in, heat up the boot on a liner heater, and slide the consumer's feet in. i inform them not to judge the fit by the exact inital fit, but by how the boot feels when they are in a "ski stance". this requires the corret buckling of the boot, which is also often a learning experience for the customer.
from this point, i usually have the customer in a boot within the first three boots they try on. the third boot i put on their foot is often the boot they come in asking for. and then they tell me the first or second boot fit better.
what is the moral of all this? when you by boots, go in with an open mind. let the fitter do his (or her!) job. do not judge until you are told to judge. and don't under any circumstances try to understand every little nuance of the process that is different from buying "cross trainers" from a 17 year old at gart's who is too busy text messaging his 14 yr old girlfriend to pay attention to his work. i buy shoes at three stores. a running store called marathon sports in harvard square, cambridge massachusetts (i wait to buy running shoes till i visit - they are that good). a clog store on mass ave in cambridge, and ski shops (and only one shop - actually i know what fits so this is redundant). all other shoes that i purchase i purchase without help from the salespeople. it's not that i don't trust them, it's that i know more about a correct fit than they will ever know. i've even had salespeople tell me to get a size 10 shoe when i never wear anything bigger than an 8.5 or european 42.5. also - every pair of shoes i have bought in my life from a "payless" type store have been shoddy, poor and fit well for about 3 seconds. i would never compare a ski boot fitting process to that. footwear sizes vary from brand to brand. they are only an indication relative to the other sizes that brand produces. it is a waste of brain power to try and convert among them.
there ARE ski boots out there that fit every conceivable foot shape. i often tell consumers that we are going to find the best possible out-of-the-box fit for them, and then make the final tweaks from there. a hard shell ski boot rarely fits perfectly out of the box, but you can get ridiculously close.
sorry about the length.