I have shrunk a hoodie, faded a print into a rumour and once ironed a mirror ball straight off a shirt. So this is not advice from above. This is advice from the laundry room floor.
The printed tees, hoodies and kids' tees
Inside out. Thirty degrees. Similar colours, which means: not with your one white towel. Skip the dryer, or use the lowest setting and accept the consequences. Never put an iron on the print. Iron the inside, or put a cloth over it, or do what I do and hang it up while it is still damp and hope.
Why your tee is not quite the same colour as the photo
Because it is garment-dyed: the whole shirt goes in the dye after it is sewn, so every piece comes out its own slight shade. That is the point, not a mistake. Two people in the same tee are never in exactly the same tee, which I find quietly romantic. The first wash may let go of a little colour, so wash it on its own the first time and it will behave from then on.
The Disco Set: shirt, shorts, long shorts
All-over printed, which means the colour sits in the fibre rather than on top of it. It cannot crack or peel. Cold wash, no bleach, hang it up. Do not tumble it, it did nothing to deserve that.
The Retro Trucker
Hand wash in cold water, air dry. Not the machine, ever. The visor comes out looking like it has been in a fight and lost, and no one wants that on their head.
The art print
Keep it out of direct sun. Behind glass the ink lasts decades, which is longer than most of the songs will be in fashion, so that is a good deal for the print.
The short version
Inside out, cold, no dryer, hang it in the shade. My mother says hang everything in the shade. My mother is right about most things, this included. The full, less chatty list lives on the Care page, and sizes are on the Size & Fit page.