My wife worked with a guy that was on a glutin-free diet, what a pain in the butt to cook for.
For me, the thing was rice. It took about a year of experimenting with different foods until I found out that keeping any food with rice out of my diet caused the symptoms to alleviate. That and dropping the drinking of a lot of sodas. I credit this discovery to my girlfriend. She really helped me get myself together.
I can tolerate a bit of rice now and then, but a few big portions and the runs begin again. :-)