Our "House Rules" for solving crossword puzzles work well to promote friendly collaboration while preserving the challenge of the sport. The primary restriction is on reference materials: they're simply not allowed. If you can remember something (e.g., the capital of Burkina Faso, or the meaning of "ort") that's fine. But it's no fair opening a gazeteer or dictionary to look things up. Research-oriented web-surfing is likewise verboten.
On the other hand, if something is in plain sight, say an author's name on the spine of a book, then it's ok to take advantage of it. Likewise it's acceptable to ask another person for an answer --- though that individual is then bound by the House Rules and cannot consult any external resources before replying. If chance should bring a clue into your field of view you are free to use that information without penalty.
Usually whoever gets to the newspaper first has the honor of doing the initial pass through the puzzle. When that person is stuck s/he passes the section along to the next victim, or leaves the paper folded open to that page for a passerby to attack. The New York Times crosswords, our favorites, start easy on Monday and get progressively more difficult as the week goes by, climaxing with a Saturday killer. (Sunday's is about at the Thursday level of effort but is larger and thus takes longer.) The Dickerson-Zimmerman group mind can generally do the first half of the week with relative ease; the later half often gets dicey and takes all day.
My inclination is to declare "moral victory" over a puzzle when its key motif has been discovered, especially once all the long thematic words have been filled in. Others in the crew want to finish off every last cell before they set it aside. Sometimes when a crucigram is deemed "unfair" we begin to alter it --- perhaps coloring in squares which are at the intersection of impossible-to-guess clues. We also scorn puzzles which rely too much on "popular" knowledge which none of us can supply, like names of TV characters or obscure foreign-language words.
When a crossword pulls a sneaky trick, such as squeezing multiple letters into a single cell, we sometimes get irate --- though if it's done with enough cleverness we temper our ire with admiration for the designer. Certain clues and answers are too cliched to garner much respect from us, like the vowel-rich "agar" or "eerie". But the worst sin, in our family book, is when a puzzle stoops to using what we call "crossword-words": cheap coinages that string together prefixes and suffixes to make a forced fit with intersecting terms. "Former moray hunter" = "exeeler"? Uggggghhhhh-ly!