I don't know if you're still looking for advice on this, but I thought I'd offer my approach to the issue. It may not work for most folks, but I'm sure there are some for whom it will work as well as it does for me.
Basically, my posts tend to be super-detailed regardless!
I love describing the scene, putting in all the extra little bits that bring things to life. So in the example given by the O/P, I would probably write something like this:
The party enters a long dark corridor, that could be anything up to a hundred yards long. The walls are damp and covered with slime and water drops from the ceiling. The flagstones underfoot are uneven, and as one of you takes a step forward the stone shifts slightly with a soft grating sound, that fortunately is masked by the constant drip, drip, drip from the ceiling. About half way along the corridor are some shadows, that look suspiciously like the band of orcs the party have been tailing for the last few hours.
It seems that you have them trapped in this narrow passageway, with no way of escape...
Note that rather than say that the orcs are 50 yards (or metres) away, I say they are half way along a 100 yard long passage. Same difference, but it flows better! Measurements and figures are given as estimates rather than exactly, and additional details are added to bring atmosphere, keep the narrative voice and help disguise the details - part of the fun of being a GM, in my opinion, is making the group work for the information, so wrap it up in the narrative. If they don't spot it, that's their problem... *evil cackle*
I hope that might help some people?