If you have any deficiencies in your diet, the body may think that pregnancy is a bit too much for it. Folic acid is important at least for fetal development. Pretty sure it's good for conception too. In any case start taking a prenatal multivitamin to make sure your body has all the necessary nutrients.
Zinc is meant to be very good. Lots of brazil nuts for snacks!
Fresh pineapple for just after ovulation to increase chances of implantation (not sure if this is just a myth though)
Grapefruit juice for increasing CM.
Also, cut out alcohol and caffeine as much as possible!
Good luck!