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.
Aside from the fact that people in your life may like that these things because they bring you pleasure. No one will ever really care about your video game trophies/achievements but you.
If no one else cares about them, then no one cares about how you got them.
If you think using a walk through or guide lessens your sense of achievement, then don't do it and accept you may never 100% the game in question.
In the end, do whatever brings you the pleasure.