There might be some good feeding schedules in the EASY forum, but in general, a 6 mo old just starting solids usually eats an average of 1-2 tsp of solids per meal. Of course, this is just an average. Your best bet is to keep a close eye on how long her nursing sessions last and her interest in each one. Breastmilk should be her main source of nutrition for several more months, so if her interest starts to decrease, then that's a sign that she's filling up on solids and you may want to cut back. She needs to still be nursing 4 times a day for awhile yet, so it isn't time to replace breastmilk with solids. Give her a full nursing, then offer solids afterward. If she'll eat them right away, great, but lots of babies need to wait about an hr to build up a tiny appetite. It's up to you when you add additional meals in...we waited a couple of weeks, but if it's going well, you can certainly add in another. Just be sure to always introduce new foods early in the day so you can watch for reactions. After you've given a new food for 3-5 days, you can introduce a new one. Pear and avocado are great first foods, as are other cereals, bananas, apples, sweet potatoes, and squash.
For consistency, it's really up to her how thick she'll take her food. You'll know it's too thick if she gags.
Poops do become less frequent and more solid once solid food is introduced, but normal varies a lot from baby to baby. You'll know soon enough...if she's uncomfortable trying to pass BMs or her poop looks like marbles, then she's constipated. The iron in infant cereal is notoriously constipating, so starting pears or prunes may help get things moving again.
