Stop Word from Adjusting Your Capitalization
The Problem:
Word keeps capitalizing words even though I'm trying to type them as lowercase. This makes it hard to create lists, write poetry, or use acronyms. I much prefer to make the choices myself rather than have Word make them for me.
The Solution:
And make the choices yourself you can; you just need to reclaim a little autonomy from AutoCorrect. More immediately, you can press Ctrl+Z or choose Edit 
Undo to undo any unwanted change that AutoCorrect has applied.
To change Word's behavior, choose Tools AutoCorrect Options (or Tools AutoCorrect in Word 2000) and uncheck the "Capitalize first letter of sentences" box and the "Capitalize first letter of table cells" box (in Word 2003 and Word XP, but not in Word 2000).
If necessary, uncheck the "Capitalize names of days" box as well; most people find this automatic correction unobjectionable, but your poems may disagree.
Scan down the list of "Replace text as you type" entries and delete any acronyms (or other entries) that you don't want to use.