I’ve mentioned it in posts before, I think. The long hours spent in a trench were mostly just going about daily routines, trying to keep one’s mind occupied.
This film gives a pretty good impression of it:
About the only major details (besides the trench being a bit too clean, forgivable because it would take many weeks of weathering to get it looking grungy and wet enough) is the fact that there’s only one actor in this. The trenches were much more crowded than that; we had the better part of an enormous modern army strung that front! It was close quarters for sure. Also, you could be guaranteed at least a small barrage most days even in a quiet sector (it certainly seemed that way at Houplines, anyhow). But yes, a surprising amount of time was spent waiting with frazzled nerves for something to happen.