my ds is 7.5 months old and i didn't start weaning til he was six months old. in our case, i wanted to give him all the time to develop his digestive system as i could as i get some IBS.
we moved from babyrice after a week, were onto two meals (breakfast and dinner) by three weeks and started with three meals a week after that... at that point i became panicky because ds was eating solids so well i worried that he was getting enough milk. then he stopped with the solids for a bit and now things are back on a pretty even keel.
long story short, i think that the most important thing is to ensure that your lo gets enough breastmilk/formula (i know between 6 to 12 months its 18 ounces a day, probably more before that) as meals are just yummy practise!
HTH!