How to make homemade baby puree?

Collect and use the cooking liquid

Cooking foods by boiling or steaming will leach some nutrients from the cooking water. Reserving the cooking water and using it to puree baby food is a great way to retain these nutrients. The cooking water will again add the nutrients to your baby's food.
Do NOT use the cooking water from carrots to dilute baby food.

Using breast milk

Using breast milk to dilute mashed baby food is a great way to increase the nutrient content of baby food while keeping it tasting familiar. Do NOT use previously frozen breast milk to dilute the purees you are going to freeze. Already frozen breast milk should never be refrozen.

Infant Formula

Freezing infant formula is not recommended because the fat will separate. This will happen when you freeze whole cow's milk. It is safe to add infant formula to homemade baby food purees that you are going to freeze. As infant formula manufacturers point out, the nutritional value of the formula is not compromised when frozen and there are no safety concerns.
Freezing an infant formula is NOT recommended. Freezing infant formula can cause changes in physical properties, such as the separation of fat, which may be difficult for sensitive infants to digest. Freezing will not extend the expiration date of the preparation. Freezing our products may cause loss of desirable appearance and functionality (but not nutrition) and is not recommended.
Another great way to slim down pureed baby food is to make your own broth. Not only are homemade broths delicious and convenient, they are also very nutritious. You can make a batch of broth, freeze it in small portions (like in ice cube trays), and use just the amount needed to thin out your baby's food purées. A delicious vegetarian broth will add great taste to mashed chicken and rice.
Remember to always consult your pediatrician about introducing solid foods to your baby and to specifically discuss any foods that may pose an allergy risk to your baby.