Good looking out for the future community, Brodie! A lot of times, people who are new to something are too self-conscious to ask for help (see me raising my hand?). This thread is going to help a lot of people from now on. I wish I'd had the cojones that you have; it would have saved me countless hours!
In keeping with the spirit of the thread title, here's a few tips I've picked up along the way whenever I start creating with an engine/editor that is new to me:
1. Create a New Folder on your desktop, so you can keep references (such as useful threads, stats tables, your own notes) quickly and easily accessible. For Grimrock, I have two tools (among others) that I keep in it, because I use them constantly (both created and generouasly donated to the community by Edsploration):
Dungeon Analyzer - invaluable tool for testing balance
Stats Spreadsheet - tabs are on bottom for different Monsters, Items, Spells, etc
2. Text files are youir friends. In your new folder, keep a text file called "things to do" (or something similar). When you get a new idea, jot it down. You'd be surprised how many things get forgotten about while you're working. Use it to jot down notes to yourself as you test your maps, too ("place mortar & Pestle in second level," "teleporter in skelly warrior room not working," "forgot to Add Torch to torch_holder in upper left corner room," "tweak timing on pit trap puzzle"...you get the idea.) I also keep a separate files for script notes (anything I know I'm going to want to add that will have to involve scripting), and a Credits text file, so I can keep track along the way of whose code I've used.
3. Find a design method that works for you. Some people map out an entire dungeon, then add mobs (monsters), items, and scenerey. Some create each room completely as they go. I work in between...I'll generally save scenery and items for the end, but I'll add monsters, puzzles and lighting as I go. They all have pros and cons.
4. Be realistic. There are some things that specific game engines can't do. The hardest thing about designing maps is having the courage to edit out ideas you really love, but either aren't working or are disrupting the flow or gameplay (balance, pacing, fun factor)...but those who
can do that, often do the best work. Use the limitations of the engine to your advantage. For example, The Duke 3D ("BUILD") engine couldn't do rooms over rooms, yet people found several ways to create the
illusion that it could. Make the engine work for your ideas, not the other way around, and you'll find both your dungeons and your skills improving.
5. STOP banging your head against the wall! I can't tell you how many times (particularly while trying to learn scripting in LoG) I've worked an hour or more on a single function, then come back to it later and it was something as simple as restarting the editor, or a misplaced word or connector. Take a break if find yourself spending too much time on one thing while getting nowhere.
6. Pay attention to your mistakes. I released a beta into the wild that was probably possible to play only by myself, because I unconsciously assumed a 100% completion by the player (because I know where every secret is and, therefore, every strong weapon or spell). Now, I've learned (after pulling it from release). I have a separate text file with a list of every item I want in a level. Toward the end of designing, I run through it and place those items, deleting them from the text as I go. In this way, I can better balance things (so 3 spell scrolls aren't in a row, for example. That also leads me to my last point (for now:
7. Assume players will only find about 75% of items in your map. Doing this will make it
much more playable.
[Edited to add #5, 6, and 7]