Wouldn't it be nice if second-hand online stores made it as easy as possible to find what you want? Some do, but Mercari could use a little help.
My credo as a writer is to "answer questions before they're asked." Here's how I'd improve an ordering page for some eyeglass lenses.
When you pick up medications at the pharmacy, wouldn't it be nice if you could choose how often to receive those papers that come with them? Here's my quick UI fix to a Rite Aid screen.
Send your users information that will save them having to do searches for information on their own, and they'll love you for it! Attach useless PDFs and they'll be annoyed.