A: Most babies do very well on basic, classic formulas from companies like Similac, Enfamil, and Nestle. Over the last several years, these companies have released advanced versions of their basic formulas fortified with DHA (docosahexaenoic acid) and ARA (arachidonic acid), fatty acids found naturally in breast milk that have been shown to help boost babies' brain development. Since these nutrients tend to be lacking in the diets of babies fed with regular formula, many pediatricians recommend going for the supplemented version if you can.
It's important to remember that the government closely regulates the nutrition in all infant formulas, and it's perfectly fine to choose a generic brand (if you compare labels, you'll find that the ingredients may be exactly the same). There's also no real nutritional difference between powdered and liquid formulas. Powdered is cheaper -- and can be toted in a diaper bag without refrigeration -- but you do need to mix it up yourself. (Although this only takes a few minutes, it can feel a lot longer with a hungry, screamy baby in the background.)