Ah yes. The most interesting part of the whole player-made dungeon thing. These are really just my thoughts on the process of making the dungeon.
Step 1: Create an idea. This is vital, otherwise, the end result will most likely be a mess.
Step 2: Build the idea. How else are you gonna export it?
Step 3: Implement the Chests and other loot. Remember to select where to place the chests carefully. Adding hidden rooms are usually good things.
Step 4: Add the mobs. I have only made dungeons which happen to be hostile, so far, so I'm no expert on adding the basic NPCs. However, I do use NPCs and NOT dummies to make these mobs. If there is a way to ADD experience drops to NPCs, it would be nice if someone could tell me... speaking of which, if you encounter a problem (I don't know if you would) generating my Jungle dungeon, move to 1.1d. I have at least one enemy wearing the full new mage set.
Step 5: ADD THE NULL BLOCKS! This is ESPECIALLY important in multi-floored structures. I'm no expert in adding them, so don't ask me much more. There's a tutorial for dungeon exporting. Figure it out there.
Step 6: Export. This is the only way you will get it to spawn. The Dungeon Exporting Guide has more clear details on how to do so.
Step 7 (intechangable with 6): Choose the configuration for your dungeon, i.e., choose what biomes or what type of biomes you want it to spawn in, what mobs you want in it, how high it generates above sea level, etc. REMEMBER: If you copy and paste the config (like I do.), remember to change the folder directory, as I forgot once.
Step 8: Share it as a Player-Made Dungeon! If you don't know how, it's simple: Toss the folder containing the config and the other essesntials into a zip file. If you don't have it, download the free version of dropbox (leastwise, that's how I do it, and, it would seem, how others do also.). Add the zip file to your dropbox. Share it to 'anyone with the link can view'. Then, get the link (the one at the top of the screen while on your dungeon doesn't work). Add a page for it on the wiki, and a link to the dropbox file, and yer done!
I was just bored...