What can I do to prepare for pregnancy if I am diabetic?

Control your glucose. It is very important to get your glucose levels in control before pregnancy as high blood sugar levels in very early pregnancy are associated with some birth defects. Please see this handout for more information: http://www.Otispregnancy.Org/files/diabetes.Pdf.
Be controlled. Do not get pregnant unless you are in good control. Seek out a high risk pregnancy group to follow you closely.