introducing solids question

I understand breast milk should be their main food source for at least a year, or at least that's what I was told. But I've recently been told to start solids since she is 6 months. How often should she eat solids? Once, twice a day? And how much? I was told only give solids AFTER she's breast fed. Any other tips? She does love to eat solids just don't want her to ever stop taking the breast!