I found a module I'd like to run. It includes some great maps. What's the best way to use them in a gaming session? They're too small to use as-is, so I'm wondering how other people use maps from modules. Do you scan and print, hand transfer the maps to a gaming mat, briefly show them to your gaming group to give them a sense of the area?
To answer your question: both.
If I think that the actual map in-book has something that would lead to a better understanding of the terrain or area, I'll allow my players a glance while blocking off areas that they either cannot realistically see or have yet to explore.
In addition to that I, and every DM I've played under, use a game mat and draw the map out onto the mat with wet erase markers. While it may not be as detailed as the in-book map, that's why I supplement the drawn one with the one in-book.
Also, I know some games come with pre-printed maps that you can use as-is. Those are really nice if you can find an adventure/module with them, but I've noticed less and less adventures have them. (Probably to save on printing costs)
Now, if the map in question is a region map, I just use it as is so the players know their relative location in scope of the adventure world, but only if it is justifiable in terms of character knowledge. If it's the area around their base of operations, yes I'd use it. If it's some new area that they are exploring and have never been to, then no. But I would have a version of said map for them that highlights the locals that they have visited.
Overall, I'd use your judgment on showing the in-book maps to your players so you don't reveal too much while flavoring your (potentially poorly) hand-drawn version.
In our group, we only use game mat, dungeon tiles or Dwarven Forge during combat as we use minis for these. The rest of the time the DM describes what they can see, providing rough approximations for distance and leaving it up to the party to create their own map as they go. As a DM I would never give exact distances and the distance I provided when describing a passage or room could be +/- 0-30 feet depending on the length of distance they could see or had travelled.
My reasoning for this is that they are not taking a tape measure or surveyors equipment and measuring every single path they follow through a dungeon. About the only hint we usually provide more often than not is where on their graph paper to start drawing and whether they should use 5' or 10' per square. "If I were to map this area, I would probably start in the upper central portion of my paper, about a 1/3 of the from the top." Or something like that.
I would never show the players maps out of the modules until after the module was over. There's too much that might be revealed that the players shouldn't be seeing or could not possibly know about "in character". If there is a need for the players to have a detailed map (i.e. in character they find one on a dead adventurer or buy one from a shop, etc) then before hand I will scan the map in on the computer, then edit it to remove things like numbers, secret rooms and so forth before giving them a printed out altered version.