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.
I have done the following:
1) Scanned a map, printed out pieces to mini scale, glued them together, and put under plexiglass. I then put sand over the plexiglass which I cleared as areas were revealed.
2) Copied a map by hand to mini scale onto butcher paper. I put my DM screen or smaller sheets of paper over portions that hadn't yet been explored in detail.
3) Scanned a map, put it on a tablet to show the players, and used a photo editing app to add a black layer on top, which I erased as areas were explored. Individual rooms were either drawn on the gridded plexiglass for minis or handled with theater of the mind.
4) Drawn only the current room on the plexiglass. Only I ever saw the original map.
I think that method 3 had the best results for the amount of work required. It facilitated both minis and TotM as the situation warranted, required no cost per map as I already had a tablet and found a free app, and takes less than 10 minutes to prepare (more if you need to edit out spoiler information such as secret doors). The players got to see exactly what I wanted them to and I could leave it on the table while still using the book.
You might be able to download maps from either the publisher or the cartographer or from a site like DriveThruRPG.
These downloads are better than those in your books because they usually include unlabelled player maps (often both gridded and ungridded) as well as DM maps. Additionally, they are electronic, so you can print them yourself at whatever size you want, or use them virtual tabletop software.
For example, Wizards have made available maps for a few classic adventures, like Against the Giants.