Specially the ones where you have to find stuff.
I usually attempt and manage to get them without looking up any info, but other times I miss something and I don't want to go thru the tedious process of re-combing whole sections of the levels, or even starting over, just to find some stupid note that I overlooked. Yet, I want the achievement, so I end up looking a guide and I feel like I haven't truly earned the achievent.
Yes, I know that playing a videogame shouldn't become a task and that I simply should play it the way I enjoy it the most, but I want too see what others think.
I never got the appeal of achievements in the first place. I see them more as friendly reminders than something actually worthwhile pursuing. Chasing them is only making things stressful and tedious, oftentimes annoying and grindy. That's kinda the exact opposite of any of the reasons I play video games for in the first place. If you want to use guides to get that 100% completion badge, do it. But if you ask me, your question means that you're letting other people tell you how to play your games on 2 different levels: first by the devs in telling you what "completing the game" has to mean for you and now, secondly, by strangers on the internet in their opinion about which ways to get there are appropriate. Play it the way you want! If you want to hunt achievements because it's fun to you, do it! And if you feel like referring to guides to get there, then do that, too!