The American Academy of Pediatrics recommends starting solid foods at four to six months. What many mothers don't realize is that the four month recommendation applies more to formula fed infants, and the six month recommendation applies more to breastfed infants. Read the first part of this article here.
If you want to be really conservative (especially recommended if you have a family history of allergies), then introduce new foods one at a time, allowing a week before introducing a new food. The older the baby, the less important this is, because he has developed more defenses against allergens. If a particular food seems to cause a reaction (runny nose, rash on the face or bottom or fussiness and gas), eliminate that food for a week, then try it again. If he has the same reaction two or three times, discontinue it for at least six months.
You may want to use a blender or baby food grinder in the beginning. If you wait until at least six months, there is no need to spend money on the Stage One, First Foods, etc. that the baby food companies spend so much money to convince you is necessary. It's easy to use a fork to mash and moisten the food you serve the rest of the family. Of course, you want to separate the baby's food before you add salt and spices. Commercial baby foods are nice for when you are traveling -- if you are eating in a Mexican restaurant, for example, you will probably want to feed him strained sweet potatoes rather than a spicy burrito.
Be prepared for a huge mess. This may seem rather obvious, but what a lot of mothers don't think about is the fact that once you start solids, you are dealing not only with wiping a messy face with green beans encrusted into your baby's hair, but you also deal with the fact that his bowel movements will never be the same. Of course, seeing how much fun he has finger feeding himself a high chair tray full of mashed banana (some will actually go in his mouth) is worth just about anything. That's another advantage to waiting to introduce solids -- you can pretty much dispense with the whole spoon feeding thing and let him finger feed himself, once he can sit up and pick up small objects. It's much easier for you (although admittedly messier) and a lot more fun for your baby, too.
Good first foods
After introducing the foods listed above, you can move on to meats (mix them with something on the list above that he is already familiar with if he doesn't seem to like it at first). Tofu is a nutritious food, and can be easily cut into soft, bite-size cubes (especially good if you are a vegetarian). Fish is an excellent source of protein, but watch out for bones.
Whole grain pieces of bread, without added egg, milk, or sugar are also good first foods.
Avoid cow's milk or dairy products, especially if there is a family history of allergies. Most babies can tolerate yogurt and natural cheeses after they are nine or 10 months old. If there is a family history of allergies, hold off until the baby is at least a year old.
Offer supplemental fluids (water and juice) sparingly. Breastfed babies don't need extra water, since breastmilk provides all the water they need. If an infant ingests too much water, it can actually cause a form of "water intoxification" which can cause the sodium in the blood to become diluted so the body can't function properly.
Fruit juice contains many empty calories, and is less nutritious than the fruit itself because it doesn't contain the nutritious pulp. Studies have shown that drinking excessive amounts of fruit juice can contribute to childhood obesity. At some point between six and nine months, many babies show an interest in drinking from a cup. Offer a little water or breastmilk (cow's milk should be avoided until he is 12 months old), and occasionally give him some juice to drink (dilute it with water in the beginning).
Foods to avoid
Foods to DEFINITELY avoid (because babies can choke on them)
Because babies' feeding skills, appetites and readiness for solids are as unique as their temperaments, individual abilities and tastes should dictate how, when and what we feed them.
Breastmilk is the perfect food for the first year of life and beyond, so just enjoy feeding your baby and don't worry about whether he finishes the whole jar of strained spinach. When you are nursing your baby, you have your nutritional bases covered. Relax, and follow your heart and your baby's lead. As long as he is happy, healthy, and growing, know that you are doing the right thing.