Hi O.,
Though many doctors say you can start feeding your baby solids (such as rice cereal) as early as 4 months, it is best for your baby if you exclusively breastfeed or give formula for the first 6 months. The American Acadamy of Pediatrics recommends exclusive breastmilk or formula for the first six months, and continued breastmilk or formula though at least the first year. The digestive tract of infants is constantly under development, so starting solids too early can lead to a lot of gastric upset, causing your baby to be uncomfortable, have constipation, or be really gassy. By waiting until she is six months, you are allowing her GI tract to develop more of the natural flora required to properly and fully digest food. Starting solids too early can also lead to a host of allergy problems, especially if there are any allergies already in your family. Some signs to look for that your baby may be ready to start solids, other than showing interest in your food and being at least 6 months old, are the ability to sit up unsupported, teeth, is at least 17 pounds, and has the ability to swallow food without thrusting it out of her mouth with her tongue. These aren't all requirements, just some signs that tell you she's becoming ready.
When my son was almost 5 months, he starting acting like he really wanted my food, grabbing for it and reaching for it. So I started giving him drinks of water while I was eating sometimes. That would help detract him from the food that I was eating, while still making him feel like he was getting something new. He only got about one or two sips a day a few times a week. He's two weeks away from 6 months now and we still do just the water thing, along with nursing of course.
You can find some good information about starting solids on the web, such as at http://kellymom.com/nutrition/solids/index.html .
Regards,
A.