Only if I am stuck for significant amounts of time. Occasionally, it ends with me going "*sigh* I'm an idiot", but most of the time its "WTF? Why would they think that makes sense? This is the most idiotically designed, nonsensical and overall FFFFUUUUUUUUUUUU puzzle/boss/route/etc ever designed in the history of video games ever" (some designers are stupid) and the very rare (Mostly from the later Myst games,) "Okay, I would never have thought to do that. Like, ever"

I also will use them to find hidden things in larger games because I just do not have the time to nano-crawl through sprawling worlds (GTA4 pigeons, I am looking at you)

yes, but that rarely happens. last time i did i think it was on a GoW:A puzzle, which was incredibly stupid.

Depends on the game

and also depends on if I'm stuck for a long time that I considering to stop playing that game, I would

Usually for collectibles to get trophies/achievements. Very rare that I would need or use a walkthrough on first playthrough, detracts from story. I would usually lower the difficulty, seeing as I usually start on normal/medium.

I use them every once in a while. For example, I was just replaying Xenogears. And I was confused on the path I had to use in the sewer portion of Kislev and the order of events. Instead of being bored and frustrated with random encounters for hours, I chose to just jog my memory with a walk-through (last time I played Xenogears was 2010.) Most modern games don't need walkthroughs though.

This i do to.

I'm currently playing through RE:CVX on my third or fourth playthrough (first time was many years ago) and in the second playthrough I got stuck in the same place at the end of the game as I did many years ago; now I know why I'm reading what people say online about the design of this game...

If you don't know how to prepare for coming events or are aware of how to take advantage of certain missables, there's a good chance you'll have to start all over again. It's frustrating because I'm really enjoying the game.

It depends on how long I've been stuck or how badly I want to finish the game. If it's a game that is heavy in story I usually try to experience it for myself, unless it's Other M where it wants me to find a tiny patch of alien blood that blends in with the grass in which case I think that it's just bad design.

I get all of the strategy guides. ALL OF THEM!