S.S.
I just went thru this for the second time with my now 7 month old. What I did was start with rice cereal mixed with a little apple juice and warm water. I fed that once a day for one week, then twice a day for 3 days, then up to 3 times a day. After that was goin well, I started green beans plus a little rice cereal for lunch for 3 days, then added sweet peas plus cereal for dinner time. Now we do oatmeal for breakfast (in a jar by Gerber) and a veggie plus a fruit for lunch, then a meat (like the jarred chicken and rice or noodles) plus a veggie for dinner. You just want to introduce one new item every few days, so that if there's an allergic reaction you'll know what caused it. So that means he eats two 4oz jars of food per meal and a lot of times after dinner he'll eat about 2oz of formula from bottle too.
I hope this is what you're asking, cause if you're asking about actual solid foods and you're past the baby food stage, this big long responce is gonna be annoying!
PS- my doc is a little on the holistic side, and she had us start with green veggies (green beans, sweet peas) then start other veggies, and make sure we had him eating all the veggies there are before we started fruits. they say babies can develop a sweet tooth and get to where they expect all foods to be sweet or they wont eat them. We did this system with our now 2 year old and everyone compliments us now on what a non-picky eater he is. He would rather have carrots than a sucker.
ONE MORE THING- my sister in law has a preemie and she says there was no difference in her diet except that she eats smaller amounts and more often. But your baby will stop eating when he's full. My theory has always been to feed them until they want no more.