A good outdoor light does something very particular at dusk: it doesn't flood the patio like an interrogation room, it just pools warm light where you need it and lets the edges fall into shadow. Run your hand over the housing of a decent fixture and it should feel solid, a little weighty, like it plans to still be there after a few winters. Flip it on and you want that soft amber glow, not the flat blue white that makes your deck look like a parking garage.
Where it goes matters more than people think. Anything too bright or too modern next to an older brick house looks bolted on, like someone grafted an airport runway light onto a 1960s porch. If your house has warm wood tones or a stone path, a stark black and white industrial fixture will sit there looking like it wandered over from a different property. Same goes for mixing finishes, a brushed nickel light by the door and oil rubbed bronze lanterns down the walkway is the kind of mismatch that nags at you every time you come home, even if you can't say why at first. Pick one metal tone and stay loyal to it around the whole exterior, porch to shed to fence line.
Scale trips people up constantly, and I mean constantly, because a porch light looks small in your hand and enormous once it's on the wall next to your door. The rule I actually use is to measure your door height, divide by three, and that's roughly how tall the fixture next to it should be, so an 80 inch door wants something around 26 to 28 inches, not the dainty 10 inch one that looked fine in a photo. For path lights, spacing is the other thing that goes wrong, people buy a pack of eight and cram them every two feet so the path looks like a landing strip, when 6 to 8 feet apart gives you pools of light with dark in between, which is what actually looks good at night. And always check the bulb temperature before you buy, because 5000K will make your warm brick look sickly no matter how nice the fixture is.
Where it falls short is anywhere you actually need to see clearly, a driveway, steps, a grill station. Decorative lanterns are mood lighting, not task lighting, and I've stubbed a toe on a step that looked romantic and lit absolutely nothing. For those spots you want a motion sensor flood or a brighter, plainer fixture, and you just accept it won't be the pretty one.
Before anything else, check the rating for wet or damp location, because a light that isn't rated for direct rain will not survive a season on an open porch.