Trying them on is important. Each manufacturer's last (the form used to build the shoe) varies quite a bit. You will find a maker or two that hits the sweet spots for your feet. If you can't get to a store, suppliers like REI and Zappos will take returns with no hassle. I've had good experiences with Sierra Trading Post too.
www.backcountryoutlet.com/ has good shoe deals sometimes and their offshoot web store,
www.steepandcheap.com has some fantastic deals, but you beeter know what you are buying there.
www.steepandcheap.com will run one item until it sells out-- that might be all day or 15 minutes. I got a paid for Salomon Canyon Mid GTX (Gore-Tex) hiking shoes there last week for $27!
I only wear Gore-tex boots in the winter when it is almost guaranteed that I will be in mud and water or snow all day. Some extensive testing was done with waterproof shoes and they take a long time to dry out once you have dunked then in a stream, or sweat soaked them. My three-season shoes have a lot of mesh and will drain and dry quickly. Not only does size vary with the maker and style, but I wear much heavier socks in the winter-- enough to require another half size. Summertime, I'm wearing light Coolmax running socks and the shoes are more of a glove fit.
Many people buy boots that are too heavy for the job. Keep in mind that you will pick 'em up and put 'em down thousands of times, so the lightest boot for the job will leave you with the most energy. Getting your load as light as possible will allow you to wear lighter shoes too. I wear trail runners for most of my hiking as my pack weight for a three day trip is around 21 pounds fully loaded.
There is a trade off between durability and weight. Long distance thru-hikers on the Applachian Trail or Pacific Coast Trail might trade off light hikers and trail runners every 600 miles or so. The inside and outside fabrics wear and the footbeds will loose their support over time-- runners have the same problem.
My personal leanings are to Vasque and Salomon foot gear. New Balance makes some very good trail runners; Montrial is another good brand. Danner has always impressed me with the construction of their boots. I steer clear of brands like Hi Tec.