Walk into a room where the lamp is right and your eyes relax without you noticing why. Walk into one where it's wrong and you'll find yourself squinting at a laptop screen at nine at night, wondering why the whole room feels like a waiting area. Usually it's not the fixture, it's the bulb and the shade fighting each other, or a base so light it's already tipped over behind the sofa.
Before you buy, check the weight of the base with it unplugged, pick it up, see if it feels like it would survive a cat walking across the console table, because it will be asked to. Check where the switch sits, a lot of them put it halfway down the cord in a spot you'll never find in the dark, and a socket switch near the top of the base is worth more than people say it is. On delivery day, check the harp and finial actually fit the shade you ordered rather than whatever generic one got boxed with it, and check the cord length reaches your outlet without a visible extension running across the floor. A table lamp is the wrong choice if you need actual task light for reading fine print or close work, most give you atmosphere, not candlepower, and if you need to see a recipe or thread a needle, get a lamp built for that job instead. Over the months, a good one just sits there and does its job through every season, warmer and lower in winter evenings, barely needed at all in a west facing room in July. The finish will tell you the truth eventually, cheap plated metal goes patchy where hands touch it, decent brass or ceramic ages into something better looking than when you bought it. Dust the shade with a dry brush or the soft attachment on a vacuum every few weeks, it holds more dust than you'd expect and it shows the moment the sun comes in low. What separates a good one from a disappointing one is mostly what you can't see in a product photo, a base that's actually stone or solid wood rather than resin pretending, a harp that's welded rather than just bent wire, a shade lining that diffuses rather than just blocks. Pick it up. If it feels hollow, it probably is.
I'd put it on a side table low enough that the bottom of the shade sits roughly at eye level when you're seated, next to a small dish for the glasses you keep losing and a coaster that's seen better days.