Staying off of the sugar and flour is crucial. Write down why you want to do this. How do you want to see yourself in 6 months, a year, 5 years? What if you don't do this? What will your life be like then?
For me, dealing with the emotional stuff that I was "running" from was almost as important as what I ate. Exercise is also a major help....do what feels good....walking, yoga, DVD's.....or what you find the least offensive ; ) Get support....this is a huge life change.....huge.