The way we did this back in the day was to create our own maps. I used the map that was included in the game as a reference (it's a jpg download via GOG) and then I would draw some generalized maps of areas. This is particularly useful in the overworld to map out forests that you can't walk through, and in the dungeons as there are certain staircases that go up/down in weird ways that are difficult to understand without mapping it out. If you want to try it out yourself, get the "Dispel Field" spell from Xiao at the Lycaeum, then dispel the fields around the ladder that leads down the Lycaeum. This layout is quite square, so it's easy to map out what the Lycaeum looks like if you pay attention to which direction the up/down ladders go.

If that's too difficult, then the alternative is to get a map that's already created. The cluebook provides you with maps (you can decline to read spoilers in the text, and just follow the map), and there are also plenty of maps online for each dungeon and area.

Another technique you can use is to use a 3rd party engine, like Nuvie and ScummVM, to look at a wider view, similar to how you might use Exult to do so. I'm actually currently doing a replay of Ultima 6 using the ScummVM engine since they recently fixed all of the bugs I reported last year, and I'm happy to report that it's a great improvement over the previous engine. ScummVM allows you to see a larger view around the Avatar, which makes for easier navigation, but could also be considered "cheating," since the original view of the game was limited to 320 x 200. You'll be able to see *way* more than you could in the original game. I prefer the "original_+full_map" view. I think by default ScummVM doubles your view to 640 x 400, but you can increase that to absurd sizes like 1280 x 800 if you want. Just edit the scummvm.ini file (navigate to your "saved games" directory and then go up one directory to find it), and under [ultima6] or [ultima6_enh], then in that section add the following:
video/screen_width=xxx
video/screen_height=xxx
video/game_width=xxx
video/game_height=xxx

FYI, for ScummVM, all of the settings are the same as Nuvie, whose settings can be found here (https://nuvie.sourceforge.net/?page=docs), but scummvm.ini uses slashes instead of XML brackets.

So in Nuvie you would have:
<video><game_width>320</gamewidth></video>

But in ScummVM you have:
video/game_width=320

Also, note that for ScummVM, the Great Light spell radius won't show you light beyond the 320 x 200 default screen size. So if you want to illuminate larger sections of a dungeon or the overworld at night, you'll need to enable cheats and then adjust the minimum brightness so that you can see more of the screen at night or in dungeons. (also, a side note, torches don't work. I recently reported that as a bug)