If you are breastfeeding then you should not start any solid foods until at least 6 months. The AAP recommends exclusive breastfeeding for at least the first six months to "allow the infant to have greater immunologic protection and limit the exposure to pathogens at a vulnerable age. This in turn permits the energy and nutrients that might otherwise be diverted to provide for immunologic responses to be available and utilized for other growth and developmental processes." (http://www.kellymom.com/nutrition/solids/solids-when.html)
Additionally, feeding readiness has physical markers such as:
*Baby can sit up well without support.
*Baby has lost the tongue-thrust reflex and does not automatically push solids out of his mouth with his tongue.
*Baby is ready and willing to chew.
*Baby is developing a "pincer" grasp, where he picks up food or other objects between thumb and forefinger. Using the fingers and scraping the food into the palm of the hand does not substitute for pincer grasp development.
*Baby is eager to participate in mealtime and may try to grab food and put it in his mouth.
Once you are ready to begin solid foods rice cereals do not make the ideal first choice, in fact nutritionally they are unnecessary. Choose nutritionally dense and yummy foods for baby instead such as smooshed avocado, banana, squash, and sweet potato. The first two choices can be mushed up with a fork and are ready for feeding. The second need to be cooked and mushed up, perhaps with some seasonings added, and make a delicious and warm meal for baby with no added preservatives.
Good luck!