I feel your decorating pain! I'd never so much as painted a room when I bought my house 4.5 years ago, but I had to learn quick. Every room was one or more truly funky colors. I'm horrible at decorating and very indecisive, so I picked a family of colors that I liked and then started trying different shades on the wall. At one point, I had 18 swatches of brown on the wall! Eventually, I made it pretty nice. I don't have two tones on the same wall but in my kitchen and great room, I painted one wall a different color than the rest. I think it's nice, and now I finally get it. I managed to tie all three downstairs rooms together, just with color.

Moral of the story is, don't be afraid to try putting some paint on the wall. If you go to Benjamin Moore or someplace similar, you can buy small amounts that are perfect for swatches.