Looking at my return from 2008, it looks like dividends and LT cap gains were separated and taxed at 15%, and the rest was taxed at 26 or 28%. Add the two together and subtract what you figured your regular tax was and that's the AMT. Or it was in my case anyway.
That's just from looking at the forms though - a lot of the numbers came from worksheets that I didn't print out. I'm no tax genius, unless being able to use Turbo Tax better than Treasury Secretary Tim Geithner makes me one.
There is no pleasure in having nothing to do; the fun is having lots to do and not doing it. - Andrew Jackson