I have a bunch of different ways I use to make maps for my tabletop game. Sometimes I draw one on graph paper. Sometimes I use Dungeonographer. Sometimes I copy a map from a published adventure or use the donjon random generators. These all have the same output: a piece of paper (or maybe two) with a map on it, and the map is usually quarter inch squares, or so.
When it's time to put minis on a mat, though, I need to copy over the relevant details of the map to our battle mat. (We use Tact-Tiles.) This is fine when most of our map is overland detail and I'm just copying down one or two rooms in which combat will occur. For dungeon crawls, where there are more random encounters or where combat can chase through many rooms, it can lead to a pretty tedious drawing of the whole dungeon as we go.
I feel foolish for having to ask, but is there some trick, technique, or something to make it less tedious to transcribe maps from printed pages to the battle mat?
EDIT: Answers in general are great, but I should note that the best answers, for me, will be informed by this previously-unmentioned fact: the game venue is not my house, so I have limited prep time on site.
Best Answer
The best way that I've seen to handle this is to draw the map in chunks. Before the session, draw the first several rooms of the crawl, either as part of your pre-game prep or as people are coming in and getting set up.
If you have a break in your session (say, to order pizza), spend some time during that break erasing the map and drawing out a new set of chunks based on the players' location.
Most of the time the layout of the map isn't actually important (since the PCs can only really see the shape of the room). If it is important, just cover the map with paper, and remove sections that covered areas explored by the PCs.
You can also print a copy of the map without details on it, and hand that to a PC. Have them draw the map as you're doing the initial narrative.
This will work well for tactical games, like D&D 3 or 4, where the players move through the dungeon relatively slowly (room to room). For games where the players might fly through rooms quickly, use a small-scale map for the overall dungeon layout, and use the battle mat for the rooms where the fighting actually takes place.