Practicing Nutrition

I'm curious how others here practice their nutrition.

I'm going to be training for my first IM this year. I've done several HIM's and have done my best to figure out nutrition. In my last one I think I finally figured out the problem of my stomach issues half way through the HIM run; it's what I eat the day before and the morning of. It seemed that the 24 hours before keeping my stores topped off was best done by consuming mostly liquid calories and eating lightly (lots of Ensure). I then had a good "movement" the morning of the race and all was good. In the past I had eaten normally the day before and just didn't "get rid of it all" the day of the race (sorry, try to read between the lines here, don't want to make this too gross, even though we all do it!).

So I guess the question is, how do you train on a somewhat empty GI system? As a normal AGer with a job and family most of my training is racing home from work or family event, shoving some food in my face and then heading out for a bike or run. Or I happened to have a larger meal a little bit before that can get me through a 3 hour ride with out having to consume calories on that ride.

I guess maybe I'll just have to be more disciplined about how / when I eat so that practicing nutrition will be similiar to race day.

Any experiences or suggestions would be great!