What can I do for my diverticulitis to avoid needing surgery?

Take care of it. First and foremost take good care of your colon. This usually entails a high fiber diet with a lot of fresh fruits and vegetables. Avoid dehydration. Drink a lot of water. Keep your stools bulky and on the soft side. Your colon will be happy. Fiber supplements like metamucil might be needed.
Diet and fluids. When talking of diverticulosis, eat a high fiber diet and drink a minimum of 80-100 ounces of noncaffeinated, non alcoholic fluid daily, more if you do strenous activity or fly in planes a lot. If you have divertiulitis, ie infected diverticulum low fiber diet and 2 weeks of antibiotics. Maintain low fiber for 4-6 weeks after resolution of symptoms the resume recommendations for diverticulosis.
High Fiber Diet. It is thought that the high incidence of diverticular disease in the us is related to our low-fiber diet. I advise people to take 30grams of water-soluble fiber supplements a day, as well as 64 ounces of water.