Make sure to get a pair that actually fit your head. They shouldn’t squeeze your temples, the ear bends should actually be on your ears, they shouldn’t slide around on your nose.

I wore glasses for like twenty years before I finally realized the source of every single problem I had with them was actually me picking the wrong frames and not inherent issues to glasses. Now that I’m aware of it I notice other people wearing ill-fitting glasses all the time.

Keep a copy of your prescription so you can buy glasses online for cheap.

Glasses fog up when you go from cold to warm. Clean the lens with soap water and wipe them off to keep them from fogging up. Or use good ol fashioned spit.

Check the screws and whatnot on the hinges periodically. Sometimes they go loose. Depends on the glasses.

They help keep rain and midges away from your eyes, so that’s nice.

The nosepads get dirty too, so wipe em down every now and then.

If you play sports and you don’t care for contacts, or if you swim, think about getting prescription googles. 100% worth it.

Take them off on the rollercoasters. Put them in your pocket or something.

Buy a spare pair in case of emergencies. This is equivalent to not having a plunger when you need one. You’re gonna regret it!

People have mostly covered the important stuff, so something less important is: if you are liable to take them off with any regularity, you’re gonna lose them on top of your head! I keep mine on pretty much any time I’m awake and not doing something specifically anti glasses (think swimming), but I know especially people who are farsighted while watching TV or nearsighed while reading will do this.

If you have to wear them constantly, like I do, remember to wipe them down with a gentle soap periodically. The spaces between the frames and the lenses will collect gunk that makes you think something is in your eyes and drive you crazy.

@paris mentioned one online retailer already but to give you another option: I’ve been using Zenni for my prescriptions for a few years now and have been happy with them.

Sometimes a vendor or optometrist isn’t contracted with your vision plan, but you can often submit for reimbursement; some health insurances (since eye health isn’t health, somehow) will also allow you to submit for reimbursement so check your policies, if applicable.

I tend to order two non-tinted pairs and a pair of prescription sunglasses when my Rx changes noticeably - one pair is made of safety polycarbonate (shatter/puncture resistant) and the other is more standard, but it’s nice to have options to choose from. As you go through them, please make sure to donate your old prescriptions! I’ve sent most of mine to the Peninsula Special Interest Lions Club in CA but there are a number of charities that will send your old lenses and frames to people who need them

Be careful when cleaning them, otherwise you’ll get scratches. Even expensive ones. Don’t use those wipes with alcohol, it’ll damage them. Either use soap and water with a clean cloth or sponge and dry by dabbing with kitchen paper. You could also get an ultrasound cleaner, which is like a little bath you just put them in. Don’t wipe them when they are not wet.

Keeping a few of those little lens cleaning cloths in convenient places is about all I can think of. They launder fine too, if you notice any become less effective at removing smears.

If you ever need a new prescription, they should be able to put the new lenses in your current frame. Similarly, if your frame ever gets broken but your lenses are undamaged, they can pop them in a new frame. That said, keeping old glasses as spares is useful, and it can be fun to have new frames.

You can adjust them, but it is better if you get them adjusted wherever you bought them because they know how to do it properly. In particular, the spot where they touch your nose might get sore, and maybe moreso on one side than the other. That’d be a sign to get them adjusted. Some people even have one ear slightly lower than the other, needing an adjustment to the arms.

Glasses have an optimum focal point so your glasses were meant to be a particular distance from your eyes and over adjusting might change that. On the other hand, the change is going to be so small that it probably only matters to the people selling glasses rather than the wearers.

Pay close attention to the fitting, tightness of the nose pads, bends of the arms. Shape all that so they won’t fling off off you look down quickly or if you flick you head to the side.

Also, be aware that they will fog up when you pass from a warm environment to a cool humid one. Or like, when you open an oven or rice cooker.

If you travel by auto when wearing tight clothes be sure to mind the extra clearance needed for your glasses when getting inside! One of my trendy larger frames took a scratch that way soon after getting them. Also don’t limit yourself to just two pairs but instead get some cheap ones to change up your appearance. Accessorize :)

Clip-on sunglasses suck, and bad ones can damage your frame or glasses. Get some cheap prescription sunglasses. Get a hard clamshell case for it that will also fit your regular glasses for easy swapping.

Also, replace nosepads every year or so and clean the gunk that collects behind it in the nosepad holder leg thingy. That thing is a gunk magnet.

If you use a computer a lot, get your optometrist to give you a distance prescription, and a “computer” prescription (which would probably be a few inches past arms’ reach). Then buy distance glasses and computer glasses. This is much better - and cheaper - than trying to do the same thing with bifocals.

For frames, I much prefer plastic. The extended nose pieces on metal frames tend to become uncomfortable, where plastic frames will just set of the bridge of the nose. Same goes for the earpieces; thin ones on metal frames can cause discomfort with extended use. Plastic frames aren’t going to have screws that hold the lenses in, nothing to get loose or lost or stripped out and unworkable.

https://www.latimes.com/business/lazarus/la-fi-lazarus-glasses-lenscrafters-luxottica-monopoly-20190305-story.html

If they get bent somehow and don’t sit properly on your face anymore, try to avoid bending them back yourself. It’s better to have a professional do it. They know where the stress points are and how to do it right without breaking them!

When you take them off at night, don’t put them lens down directly on furniture or anything like that. You will scratch them. You can either set them on a microfiber cloth face down, lay them the other way (lens up), or get a glasses stand if you’re feeling fancy.

You could use your glasses holder, which is what I do when I travel, but I find that being able to access my glasses quickly is more valuable to me.

Also I get discount glasses from Zenni, Costco, or Eyeglass World. I never get just one pair because I am forgetful. If you can swing it, I would get at least one backup pair.

When you get a new prescription, you can keep one pair of the old glasses in case something happens to your current pair(s). (The plan being that you will not be completely screwed, you’ll have a “close enough” pair until you can rectify the issue.) If you do that, store them in a case and label the case with the date you got that prescription. I would only keep at most one backup from your old pairs.

If you work in an environment where you go from cold to warm and they fog up often, you can get antifog treatments that don’t last forever but do help keep them clear.

Buying a few pairs from cheap online sellers like goggles4u can save you a bunch of money. The antiglare coatings are applied to almost every lens already so don’t bother paying for more coatings.