Style
Super-cheap watches look cheap and childlike. Bright colors, basic ugly LED displays, or chunky watch hands.
But if you prefer a more elegant look, it only costs a few bucks more to get something well-designed and tasteful. Digital is okay for casual wear, and a good digital watch may be helpful for some sporty purposes, but you'll want an elegant analog when you're dressing up. Formal occasions also call for subdued styling instead of gaudy colors. You pay a little extra for these things, but not much.
Materials
The quality of materials used does affect the look and feel of the watch substantially, but you can easily spend an extra $30 on a better wristband.
Wristband
The type and quality of the wristband can affect the look of the watch, its durability, and how comfortable it is to wear. Bottom of the line watches have plastic wristbands, which can be damaged easily, and feel cheap. They are also not very breathable. However, they are unlikely to irritate your skin.
For a more money, you can get metal links, or a fabric or leather (or fake leather) wristband.
Fabric or fake leather may look a little better than the plastic, is (just barely) suitable for more formal occations, and may be a little more comfortable and breathable than plastic.
Real leather (and at the high end, genuine alligator skin) looks better than fake leather, may be more breathable, and matches a formal outfit. If you are really dressed up, you want real leather, not fake leather or plastic.
If you go for metal links, you can either get the stretchy kind or the loose kind.
The stretchy kind is likely to pinch, and the links are prone to breakage. However, it can easily accommodate a range of wrist sizes, and stands up to day-to-day wear okay. It is a good "sporty" look. I would try to avoid wearing it to weddings or funerals.
Loose metal is considered a little fancier than metal stretch bands. The weak point of loose metal links is the clasp, which is the most delicate moving part of the band. In addition, the quality of metal matters. Some cheap metals can irritate your skin. In addition, more expensive metals may look prettier.
There are a wide range of metal band options, with a wide range of prices. But no one will think you're underdressed if you find a loose metal band made with real metal, that doesn't irritate your skin.
The Body of the Watch
There are plastic, painted-plastic, and metal watch bodies.
Plastic is pretty durable and will only suffer minor discoloration over time.
Painted plastic may look like a metal body at first, but it will show the material underneath as the coloration wears off.
Real metal looks better for a long time. It doesn't need to be an expensive metal - brass bodies wear just fine - but more expensive metals do look fancier to a trained eye.
Thinness
It takes a little more effort to fit a watch into a smaller body, so thinner watches are a little more expensive. But thinner watches are less likely to catch on your sleeves or anything else, can feel lighter and more comfortable, and look more elegant because they continue the line of the wristband.
If you have a metal band, there's no need to get a watch thinner than your wristband.
Motion
"Swiss action" doesn't mean anything. Nobody cares. Watch guts take two forms: quartz, and pure-mechanical.
Most watches use quartz to keep time. Quartz is quite accurate, but if you have a second hand, it will tick once per second. There's nothing wrong with this, except that it means your watch is cheap.
Mechanical-action watches are more expensive, but if they are especially well-crafted, you can get the hands - even the second hand - to move continuously, at least as far as the unaided eye can detect. This doesn't make your watch work better, but it can be kind of cool to watch, and shows you spent money on a "good" watch.
Extra-fancy mechanical watches sometimes allow you to wind them up, or even charge them by the day-to-day motion of your hand wearing the watch. There's no real advantage to these other than coolness. But that's okay! If you have the money, why not get it because it's cool? If you just needed to know the time you could use your cell phone; watches are for style points.
Function
Some watches can do more than others. A more expensive watch might include a stopwatch, barometer, or date function, or keep time in more than one time zone. You might also pay more for water-resistance, although some quite cheap watches are pretty good in light water as well.
Buying a Watch
So what kind of watch do you want? It depends what you'll use it for.
If you are doing sporty things, then you want a practical watch, and probably don't care much how it looks. First figure out what functions you need (waterproof? stopwatch? shock-resistant?), then find a comfortable watch that does all those things.
If you want a watch as an elegant accessory when getting dressed up, it pretty much has to be analog. I recommend at least a real leather strap (unless you have ethical objections, in which case a loose metal wristband is fine), and a brass body. Quartz action is fine, and no one will sneer at a watch that only does one thing, well: tell time. In fact, more functions is probably not a good thing, especially if you don't understand them.
If you want to show off your money, you can do two things:
1) Get a watch with mechanical action that quartz can't replicate, i.e. the smooth motion of the second hand. Or functions only found on expensive watches, like a barometer or fancy types of date-tracking. Hand-wound or motion-powered watches also have that "cool" factor.
2) Get a watch made of fancy materials. Precious metals in the wristband or body. If you really want to show off, you can get one with precious stones, but this can cross over from fancy to gaudy if you're not careful. I would suggest erring on the side of subdued if there's any doubt, but it depends on whom you want to impress. You know who they are. I don't.
Maintaining and replacing watches
Many jewelers and fine watch stores will replace batteries for free. If your watch stops, it can't hurt to ask.
If your wristband breaks, or looks too cheap for your taste, you can get a new one. Most watches will accommodate any wristband style: metal, stretchy metal, plastic, fabric, leather, or alligator-skin. Don't bother with a style much better than the body of the watch itself. If it has a plastic body, don't go with fine leather. But a nice band can do a lot to improve the look or comfort of a watch, and give it a new life.
Unless your watch is quite expensive (well over $100), or under warranty, don't bother getting repairs done to the body of the watch; just get a new one.
