The Creation Kit tutorials offer a host of various tips, tricks and guides on how to get the most out of Bethesda's modding software.
In today's tutorial;
Adding clutter to dungeons, including slightly more advanced ideas such as levelled items, dummy items, locked containers and more. Note; when you load up an already made dungeon (Even if it's one you made) make sure you set it as the "Active File".
Link to my ready made dungeon - http://skyrim.nexusmods.com/downloads/file.php?id=8508
Creation Kit Tutorials Playlist - http://www.youtube.com/playlist?list=PLE3E7CC13B95E5AB6&feature=view_all