I like doing crosswords. More specifically, I like doing the New York Times crossword on Monday and Tuesday, and sometimes Wednesday. Monday is pretty easy; I can always complete it. Tuesday is a little more challenging, and by Wednesday there's an excellent chance that I won't be able to figure it all out.
Doing the New York Times crossword was a challenge of mine a couple years ago and I bought a book on conquering it. From this book I learned that each day has it's unique character - Monday is designed to be approachable and finish-able. Tuesday is a little harder, Wednesday even harder. Thursday is wild card day, so you may need to figure out that some boxes require double letters, for example. One Halloween you needed to draw little ghosts in some of the boxes in order to solve it. Friday is very hard and Saturday, too. I don't remember if there was anything else special about them. Sunday is a much bigger puzzle, about as difficult as Wednesday.
Using the book helped me learn how crosswords work, and the usual small words and their clues that repeat a lot. I really did get better, though I haven't conquered it yet.
Some people recommend doing crosswords as a way of staving off memory loss and even dementia. I don't think doing crosswords really helps with either of those. I think doing crosswords make you better at doing crosswords, which is all I'm looking for in these puzzles. Sometimes I learn some new vocabulary or a new fact, but mostly I just enjoy the challenge of filling in all those little square correctly so the whole thing fits together perfectly. Aahh.