D.M.
I started with rice and oat cereal at 6 months, I think our Pedi said it was best for the adjusting belly to start with something basic and work up to the veggies and fruit. For us, bananas constipated my son as an infant and I always had to combine it with apples or pears.
We started with one feeding in the morning for the first week or two, and then added lunch and then a couple weeks later added dinner. At this age/stage you need to start gradually and only add one new food at a time to be able to monitor any allergies and/or intolerance for flavor or taste. It wasn't until about 9 months that we were into a 3-meal day, and I still breastfed on demand and before meals per my son's Pedi.
This link was my best friend during this time:
http://www.babycenter.com/0_age-by-age-guide-to-feeding-y...
Just remember that an infants digestive system is fragile and needs the introduction period to the food before jumping into it full force. I found out SO many things about my sons ability to tolerate foods, and which ones would cause gas or upset his tummy. Do some research and ask your kiddos doctor if you have concerns about how to start his diet...
Good Luck!