Here is my .02:
Ideally a bootfitter is the way to go, they specialize in this and are worth it.
Your next best option is to find a reputable ski shop. There are some things you need to look out for here. First check reviews to make sure they are experienced in what they do etc. Then call the shop and ask what employee is best at fitting boots, there is usually one guy there that knows what he is doing. Dont get a 23 yr old bro for this, the general rule of thumb is the older and crustier they are the better. Also ask when that employee is working and they are not busy. If you walk in to get boots and there are crowds there just turn around and walk out, its not worth it. Its not a bad idea to call the employee and let him know you are coming in to get boots, this will go a long way to getting the attention and patience you need to do this right.
So you found a good time to go in and there are hardly anyone at the shop. First off, make sure you bring you ski socks or buy the kind you want there and fit your boots with them. Dont use the demo ones that have. Find the employee and go to the boot section. You will see a whole bunch of boots on the wall with different brands and colors etc. IGNORE BRANDS, COLORS and DESIGNS! The worst thing you can do is get your heart set on those cool looking green Solomon boots that dont fit your foot but you try to ignore that because they look sweet. Then at 9:45 am on your second run you are going to hate yourself. Talk to the guy about how you ski and work out a budget and what stiffness you need. Then take your time and try on every boot that fits your parameters, I mean all of them. Out of the 5-6 you will try one or two will really feel 'right'.
Buckle them on and walk around the shop for about 5-10 min, look at jackets, skis or whatever. There are sometimes fit issues or discomfort that often dont come up right away but you will notice after a few min. Also, imagine your skiing and feel how the boots flex on your shins etc. If they feel good and you like them ask the shop to heat mold them for you, it will help make that good fit into a great fit but it cant fix a bad fit.
So that is pretty much it. Remember this is a big purchase and will make or break how you enjoy skiing so really take your time. I can pretty much grab any kind of ski on any day and find a way to have fun but if you boots dont fit you are going to be miserable. You will also be that dude in your ski crew that has to unbuckle his boots on the lift every run and make them wait for you at the top to buckle them down again which sucks.
