The print tells you everything after enough washes. A good one fades evenly and stays soft without cracking into little dry flakes across the chest, a bad one goes patchy after about eight washes and you end up with a shirt that looks like it survived a fire. You only find this out weeks in, long after the receipt's gone, which is why it's worth knowing what to check before you've handed over any money.
Keep it away from anything else with a loud pattern or a slogan of its own, two busy things on one body just read as noise, so let the bottom half do nothing at all. Plain jeans, a plain skirt, trousers in black or navy, that sort of thing. For colours and finishes, the easiest shirts to live with are the ones on a heathered or washed out base rather than stark white, because white shows every faint mark and every wash line around the print, while a soft grey or a faded black hides the small stuff and still lets the graphic read clearly. In the shop, stretch the fabric gently across the print and look at the edges, if you see tiny cracks starting already, that's the print lifting before you've even worn it once. Check the neckline too, a ribbed crew that holds its shape is worth more than it looks, a floppy one will be stretched out and gaping by the third wash. And always check the side seams sit straight down rather than twisting round towards the front, because a twisted seam means an uneven cut that will annoy you every time you put it on. The difference between one that lasts and one that doesn't is almost always in how the print is applied, a print that's been properly cured into the fabric has a slight give and a matte finish, while a cheap transfer sits on top like a sticker and starts to peel at the corners within a month, usually right where your bag strap sits. Heavier cotton, around the same weight as a decent sweatshirt rather than something see through, tends to hold the print better and doesn't go translucent under the opposite room light at work or wherever you happen to be stood.
It's worth buying the size up from your usual fitted tee too, because graphic ones are meant to sit a little looser, and a tight one makes the print stretch and distort across the chest in a way that looks accidental rather than deliberate. Once you've got one that's held its shape, it makes a plain pair of jeans you've had for years look like you just put thought into getting dressed.