I've been fortunate enough to talk my friends into playing a Planescape campaign for some time, though as the resident Planescaper among us, it has fallen to me for some time to DM. As a 2nd-editioner with extensive access to Planescape sourcebooks, I have access to all the pretty pictures and flavor text on the wonderful planes and their lovely locales. Nearly all of my players, however, have none of them, and in fact only one played Planescape (not simply Torment) during 2nd edition. How--and bear in mind that I play mostly online since my regular gaming group is split up at school--can I really make sure that they really feel like we're in the planes?
I want my players to be able to look back and feel like they know what it would be like to explore Pandemonium, for example. Or Mechanus. Or even simply what it would be like to go shopping in the Market Ward. Right now, my main tactic is providing paragraphs and paragraphs of description, but I feel like, in violation of the "less is more" paradigm, much of my blathering is lost and doesn't really contribute to their understanding.
What else can I do? I feel like I'm constantly stripping things down to their barest forms to make sure that anything they see or do is as close to the prototypical experience of whatever it is they're doing. I feel like if I don't include something in an adventure, it won't be part of their Planescape concept.
What do you all do to achieve this kind of shared experience?
Hmmm. I think the key here is not so much to try and pare down the initial description, but instead work to break it up - getting several aspects of the place, and throwing them at the players one at a time, letting them react to each in turn and building up the sense of otherness.
For Gehenna, frex, the first thing they get hit with straight out of the portal is the choking smoke, seeking to smother them. Make them worry about that, take some action to deal with it, and only then pass on the sullen lighting of the place. A ways further on, earth tremors that threaten to knock them off their feet, or razor-sharp basaltic rock that threatens to slice their feet to ribbons.
In each case, it's one small element of the plane, presented on its own so that PCs can seek to adapt or respond to it. Taken in sequence, you've got a very different place than the Prime.