Babies usually start eating true solid foods just around six months, and it's not recommended they start before that. There are many reasons for this, but in a nutshell, it's about baby's digestive tract being fully developed, choking hazards
, allergies, and the simple fact that you could overfeed your baby. They just don't need that much food and the difference between breastfeeding and formula versus foods is that they can tell you, by stopping, when they're full. With table food, they may not show you that sign until too late.
Note that babies who are not full-term infants may experience delays in their development and this can be especially important when introducing foods. See your doctor for more information in this case, because I'm completely out of my league here.
Allergies show up in different forms, such as diarrhea, throwing up, a rash (diaper or other), or even coughing. You have to watch your baby for any unusual behavior and the times that the symptoms occur, because she can have her own reaction to things her body can't take. Remember, though, that gagging doesn't indicate an allergy. It's a reflex, and it's common when babies start to taste new foods.
Whatever you do, don't gag yourself when tasting your baby's food in front of him. Lesson #1 in food introduction is that babies follow the philosophy "Don't expect me to eat anything that you won't eat."
Signs that baby is getting ready for solid foods are when she can sit up, hold her head up, allow tasting food with a spoon, and when she can begin to show you what foods she likes.
Babies usually will like foods their parents like and we need to try it, try it again, and try it again with them in order for them to develop the taste. Developing a liking for foods includes getting used to the flavor, but it also includes getting used to the odors and the textures.
The key to introducing solid foods is to decrease formula or breast milk, etc., during the day. Baby has to be hungry and without view of their "old reliable" bottle or breast. If you are normally "lunch," you might have someone else feed your baby for a short period of time until baby adjusts.
As soon as baby can sit up, feed solids in the high chair. Even small babies understand and enjoy it when they are allowed to do things that bigger people or other babies do. Somehow, they just know they are growing. These things, like sitting in a high chair, become accomplishments to them even if they are a bit afraid of it at first.
The goal is to get baby on the same meal schedule as you are. In the beginning, you may have to eat breakfast a bit earlier and dinner a bit earlier, but you can deal with pulling baby into your normal dining schedule once baby starts liking the foods and as she starts to stay awake longer.