When we first started we just did solids once a day, generally in the morning. Then after a few weeks added lunch. By 7.5-8 months we were on three meals a day and added snacks came later. I used to be quite worried about amounts and gave 1-2 ice cubes of solids per meal but after a while I realised she would stop when she had enough so didn't worry about quantity too much. The trick is to make sure it's not interfering with the amount of milk they are taking. We did drop from 4-3 milk feeds about 9 months when there was alot of dairy in her diet. My DD1 really liked solids and did eat a fair bit without milk being affected. We did finger foods from early on too!
HTH xx