Straight cow's milk is not appropriate. Some infants do better on soy based formulas because of a sensitivity, allergy or potential allergy to cow's milk. Some infants are also sensitive to the lactose or sucrose used in the formula, so consult with the infant's pediatrician if the first formula you choose does not seem to be easily digested by your infant. If there is a strong family history of food allergy on either side of the family, it is advisable that the baby be fed solely breastmilk for the first six months of life. Research has shown that babies with a family history of allergy who are formula fed or supplemented with formula, have more food allergies than infants who are fed breastmilk alone.
Prices vary widely and formula can be very expensive.
Both liquid concentrate and powder need to be mixed with water before use. Be sure to use very scrupulous sanitation practices and to follow the directions on the can carefully. Infants can run into medical and growth problems from under or over diluting the formula. Liquid concentrate is the most popular form, because all you have to do is mix with an equal amount of water. If you have well-water, or are concerned about the safety of your water, have it tested by your local health department or a reputable lab, before using it to make formula.