Are there any procedures or habits I can adopt if I need to fly and I have some GI problems?

Imodium (loperamide)? If you mean that you are prone to diarrhea, then taking an Imodium (loperamide) before boarding the plane should help;.
Please be specific. Please be more specific about your GI problems. What are your GI problems? Diarrhea? Constipation? Hemorrhoids? Vomiting? Ulcer? Food allergies or intolerance? Bleeding? Inflammatory bowel disease? There are different precautions for each of these.