Many, many pediatricians and moms (and others!) are still operating under the old information to start babies on solids early (like 6 weeks, 3 months, etc). I'm not talking about babies with severe reflux or some other medical condition - I'm talking about your average baby. So many babies are being started waaay too early on solids. The actual medical research shows that babies who are ready for solids can do the following:
* sit up well unassisted
* have a good finger-thumb pincer grasp
* perhaps have teeth
* tongue thrust reflex has lessened
Better to follow your baby's signs than watch the calendar!
For more details, links to current medical research on solids:
Medical research shows that it is healthiest for the MAJORITY of a baby's nutrition for at least the first 12 months of life to come from breastmilk (ideal because of the immunological benefits, reduced risk of cancers for both mom and baby, and reduced risk of obesity for the baby) or formula (2nd choice - we're lucky to have a 2nd choice, though it'd be healthier for ALL of us if moms had more support for breastfeeding from their pediatrician, their friends & family, and their workplace).
Bottom line: for the first 12 months of life, breastmilk or formula should be the BULK of a baby's diet, with solids thrown in for supplementation, experimentation, social time at the dinner table -- starting when the baby shows the signs of readiness.
Your baby is just 6 months old, so if he's sitting up well, has a tooth, is able to pick things up well with his thumb + first finger, and doesn't thrust food out of his mouth when offered via spoon, he's ready to try solids - but definitely the good majority should still be breastmilk/formula.
Congrats on your baby boy - 6 months flies by, doesn't it?