If you mean for mapping a dungeon, just describe it and let them map it on a piece of paper if they want a players' map. If you mean for combats, really, it's just a question of describing the scene well and the players giving clear indication of what their PCs are doing. You don't have to go into excruciating detail, but things like the approximate dimensions of the area they're in and what's inside it is enough to be getting on with.
I have a lot of minis, so I like using them, but sometimes just letting folks use their imagination is a good way to go. LL doesn't require you to track what square/hex everyone in is or worry about things like flanking, so the game doesn't "suffer" for a lack of grid & minis.
If you have time to watch a long-ish video, check out Wil Wheaton's "Tabletop" on Youtube where he plays a PnP RPG sans minis, etc.
http://www.youtube.com/watch?v=Y-61i3R5y9Y