The book that dakotagirl recommended is very informative; I would suggest it even if you feel like you know a lot.
I would also recommend doing a food journal for a month or so. UC is a very individual disease, so diet differs for everyone. Also, doctors don't spend much time researching diets, so there's not just one diet that we know of that can help or cure UC. After keeping a food journal, I realized that I can eat just about anything as long as it is in moderation, and I just try to keep spicy, fried, and sour foods to a limit. If bleeding is not much of a problem for you, then some of the symptoms to look for would be looser stools and cramping.
Female, Age 19
9 Asacol, Rowasa, 1000 mg Canasa, Proctofoam, Rifaximin 2/day
Digestive Advantage (Crohn's & Colitis), 1 Florastor, 50 mg 6MP, 1 Primadophilus reuteri, Remicade (4 infusions), 2.4 g Lialda, 1 Forvia, 6 Colazal/day, 1 Anucort