Eat 5 portions of fruit and vegetables a day - it is so important to get all the vitamins and minerals your body needs and mix it up as much as possible. Try different fruits and cook with different vegetables to add more variety.
Don't go food shopping when you are hungry. This is a bad idea when on a healthy eating regime as you will be tempted to buy more food and food that is not so good for you!
Do not underestimate the power of walking as an exercise to keep fit - even new mums can get out there and push the pram / buggy and work out. Join up with other mums or friends so you can exercise in a group and support each other.