Read Good Books!
What you are reading will greatly shape your thought processes throughout your pregnancy. I recommend books that educate you about all that is available to you. Books that give you different view points. Don't take your doctors word on everything. they are only human and you know yourself far better than anyone else.
My favorite book list:
Pregnancy, Childbirth and the Newborn - Simkin, Whalley & Keppler
Active Birth - Janet Balaskas
The Thinking Woman's Guide - Goer
Ina May's Guide to Childbirth - Gaskin
Birthing From Within - England
Husband Coached Childbirth - Bradley
The Nursing Mother's Companion (This is a must have BEFORE you give birth.) OR The Womanly Art of Breasfeeding
Eat Healthy Food!
Eat a balanced diet. A diet over heavy in carbohydrates could cause gestational diabetes (include bread, rice, potatoes, pastas, fruits). Eat some from EACH food group at every meal.
Avoid processed food (or eat in moderation). It is high is sodium and bad for your baby.
Eat plenty of protein. It is recomended to get at least 80 gr of protein each day. Protein contains the building blocks of life and helps to develope a healthy placenta that nourishes your baby. It also helps your body to prevent pregnancy induced hypertension.
Drink lots of water. Your body needs that water to maitain proper function. Get at least 2 L each day.