I have trouble holding my camera level, especially when I hold it vertically. Even when I try to use the autofocus points as a reference, I usually come out a little slanted. I really don't enjoy rotating and cropping my photos in Photoshop because I usually frame the photos with the exact focal length I need. Plus, I can't stand trimming pixels off my 10.1 megapixel images.
What are some ways to improve holding my camera level? (besides buying a Canon 7D)