A player reaches for a strategy guide or FAQ when the fun-factor of a challenge is overcome by frustration. This can happen most frequently when a collection quest becomes monotonous, or when a puzzle or challenge becomes so difficult that the player stops having fun trying to figure it out on their own. As with most things having to do with fun-factor, personal tolerances can vary wildly between individual players. However, there are general concepts that are worth looking at.
100% completion of collection quests has to be one of the biggest causes for looking up a FAQ. There is a reason that Zelda and Pokémon games have permanent spots on the top ten FAQs list on GameFAQs. The problem with completion quests is that sooner or later, you have scoured every place you can think of, and are inevitably missing 2 or 3 of the items you need. In any collection quest where you are asking someone to look for more than a handful of something, you can expect that no matter how easy it is to find the objects, someone might just miss one and assume that they thoroughly swept the area.
There are two ways to control how much someone needs to consult a FAQ for a collection quest. First off, a developer can limit frustration by requiring the player to collect less than 100% of the items. This doesn't stop the problem completely, but it does put off the problem of needing to track down the couple you missed until later, usually the post-game period. Of course, there should be an additional reward for 100% completion, to avoid the player feeling like their effort was fruitless. However, this approach doesn't work for all kinds of collection. The second way is to limit the benefit of a FAQ by giving the player hints of some kind in the game. A pair of examples of this are in The Legend of Zelda: Twilight Princess. In that game, you can purchase clues to the general location of heart pieces from the fortune teller. This makes tracking down elusive heart pieces much less tedious. However, I thought its explicit hints might have made the quest too easy overall. I actually prefer the implicit hints found in the golden bug hunt. The implicit hints for the golden bug quest came from their pattern: the bugs came in pairs that were always found in the same general area, and were scattered somewhat evenly across the game world. A pattern like this can work just as effectively as a blunt hint with the added bonus of being fun for the players as they uncover the pattern. The trick is to make the pattern consistent and logical enough to figure out and be extrapolated.
Making it so that puzzles don't send players scrambling for a strategy guide is a trickier problem to balance. If you make the puzzle too easy or the hints too obvious, then the puzzle doesn't challenge the player, which means the player probably is bored. However, if the puzzle is too hard, then it sends players straight to GameFAQs. Figuring out how to put a puzzle in the butter zone is tricky. However, the key often involves a gradual stepping up of difficult of puzzles. Start with simple puzzles that teach the concepts to the player, and then move up to increasingly complex variations. If the player is familiar with all of the basic elements of a puzzle from past experiences, then they are more likely to be going to be able to solve it on their own.
Hmm, I should probably talk more about some of these topics in later posts.