Hiking footwear selection is a highly personal, trial-and-error, context-dependent endeavor. Before purchasing shoes, it’s important to consider questions like the following: What sort of hiking do you anticipate doing? How many hours (or days or weeks) and miles at a time? How much weight will you be carrying? Across what sort of terrain will you hike (e.g. well maintained packed dirt trails, muddy bogs, rocky and gnarly bushwacking, etc.)? In what conditions (scorching heat, freezing cold, torrential rain, etc.)?
And then there’s the personal fit — how wide are your feet? How tall are your arches? How muscular and stable are your ankles and feet? How roomy a toebox do you prefer? Are you more concerned with preventing blisters or wet feet or rolled ankles, etc.?
In recent decades there’s been a push away from big, heavy hiking boots and towards lighter, less supportive shoes (somewhat paralleling the fall of bulky external frames and the rise of internal frame ultralight backpacks). A lot of people I know hike and backpack exclusively in trail runners, with some even opting for only minimalist shoes or hiking sandals (all of which I’ve tried myself for a few years each). Ideally, you’d get a few different pairs that you could whip out under different conditions. If you’re looking for a single type of all-purpose shoe, so-called “hiking shoes” or lightweight, low-cut boots would be your most versatile choice, imo – not too uncomfortable on flat, gentle trails, but with good traction and support on slippery, rocky hikes. I’d generally also recommend against getting EXTREMELY WATERPROOF sorts of shoes — in my experience, they end up being really hot so my feet sweat under dry conditions, and when it rains, they inevitably get wet and take forever to dry out (granted, the latest, high-end ones may be different — I feel Gore-Tex is always coming out with REVOLUTIONARY NEW MATERIALS). It’s generally preferable to get something lightweight, too — “a pound on the feet is five on the back” is a popular saying in hiking circles (of course, try not to get frostbite wearing by wearing trailrunners on a backpacking trip in freezing rain and snow. It is, let’s say, not very pleasant).
As for actually buying shoes, I think the best approach is to crowdsource (look at amazon’s and other online retailer’s top rated shoes), and read the reviews to find the ones written by people most like yourself. If you’re a wide-footed man with small, delicate feet looking to do 10-20 mile hikes in temperate forests and all the top rated reviews are by women with extremely narrow, calloused feet who’ve only ever gone on 2 mile nature walks in Antarctica, their experiences might not adequately represent your own. Also, look at outdoor gear magazine recommendations (e.g. like those suggested by Backpacker Magazine). When you have a solid 5-10 contenders, head to an outdoor gear store like REI wearing the socks you’d wear for hiking (and ideally after already walking around a fair bit, in case your feet swell substantially during activity) and try your pre-selected pairs on. Be sure to walk around the store a good bit in each pair with your pack loaded and step up and down off of their chairs/benches to simulate real-world hiking.
The shoes shouldn’t feel uncomfortable here (on the trail after several miles they may, though that might be because you need to break them in). How tight they should be is a tricky question — some shoes (especially ones with an all-leather construction) will stretch to accommodate your foot as you break them in, so you might opt for a slightly tighter pair. If you neglected to pre-hike and know your feet swell a lot after 1-20 miles, consider going for a slightly looser pair. Ideally, your shoes should allow for minimal slippage under trail conditions (since slippage = friction = blisters, or worse: rolled ankles, falls, etc.), but not be so fitted as to restrict bloodflow or be uncomfortable. Luckily, laces can be tightened or loosened to result in a (narrow, but important) range of fits (see below for information on lacing patterns).
Then, when the store manager threatens to kick you out, either buy your top shoes to appease them (REI has a great return policy IIRC, if the shoes aren’t comfy in actual practice), or, if you’re a cheap asshole like me, take note of your favorite model and buy it online for typically much less (newer models can be competetively priced with REI’s regular 20% off coupon though). SierraTradingPost.com has been my favorite site lately for new outdoor gear — they sell the last several years’ stock discounted, and if you sign up for their mailing list, once every few weeks they’ll send you a 40-45% off coupon, so you can usually snag things for 60-80% off MSRP [EDIT: recently they seem to have cut back on their super coupons, with the highest coupon discounts offered skirting, at most, 25%-off with free shipping. Still solid deals though). The people in the shoe section at an outdoor gear store can occasionally be helpful, too (they’ll often have some outdoor experience themselves, if not always a lot), so you might benefit from asking them for advice. But if you take up a lot of their time, OFC consider buying something from the store.
Additionally, I’d recommend a proactive approach to blister prevention (if I anticipate getting any, I’ll pretape blister-prone spots with leukotape on the flats and micropore on the toes, which has worked great so far. You can see more good recommendations here). I’d also advise that you pick up some orthotic inserts – if you know your specific foot requirements (e.g. high arches), you can get a pair intended to accommodate them, or you can get some custom fit ones (I have some you put in the oven for 10 minutes and then wear cold so they mold to your feet). If you want to go all out, a podiatrist can make you some for a few hundred $, but the $20-$30 options on amazon have worked well for me.
Some lightweight gaiters might also be useful — not the waterproof sort (though in some conditions those are invaluable), but the breathable cloth ones. I use the “Dirty Girls” brand, and they’re great for preventing dirt and sand and stuff from getting in your shoes (esp. if you’re wearing shorts), which is also important for maintaining clean feet and preventing blisters. You can also look into “sock systems” and sock liners and stuff, though I personally don’t use them (my feet get too hot and I don’t get blisters with the aforementioned prep). For socks generically, though, I really like Costco’s Men’s Trail Socks for the price (the smalls fit Kate, and I think the men’s fiber composition is nicer than the women’s specific one), though they’re definitely too thick for the summer. You want to match the thickness of your sock and shoe to weather requirements, because hot, sweaty feet are not only uncomfortable but can accelerate blister formation.
Ooh, and crocs make for my favorite middle-weight camp and river-crossing shoes, and hiking poles might be worth looking into too (they’ve saved my butt a few times on steep, slippery descents; Costco again carries some good, inexpensive carbon-fiber ones).
Once you have some shoes and have worn them for a while, consider further customizing lacing pattern to suit your personal needs. There are many ways to tie shoelaces that can help alleviate foot problems experienced while hiking. Here are a few (from Iowa State University’s Department of Food Science and Human Nutrition):
All in all there’s a fair bit to consider, but perfect’s still the enemy of good enough, and usually the problems are sufficiently minor to not bother worrying yourself too much. Even if whatever you get is suboptimal, you’ll better know your preferences when it’s time to buy shoes again! Hope that helps and happy trails!
(side note: afaik there have been some basic attempts to evaluate the influence of shoe selection on injury, but I’m hesitant in interpreting their results without access to the raw data with which to perform my own analysis)