When I started trying to cook/eat better, I started with one small substitution:
Replacing white/processed flour w/ whole wheat or whole grain
It's really so easy to do. I still keep regular flour around for when Steven wants to bake cookies or something like that but even then, you can do 50/50.
Start by looking for whole wheat spaghetti noodles, pasta noodles, wheat bread, wheat tortillas and brown rice. I can tell no difference whatsoever!
You do have to be careful with labels though--just because something says whole grain doesn't mean it's 100%. When looking at labels you should never see the word "processed", "refined", or "bleached". A lot of things (including pastas/noodles) claim to be whole grain but if you look at the ingredients it usually contains the words durum or semolina somewhere in there which means the entire grain isn't used. I still haven't found a 100% whole wheat pasta so if you find one, let me know! Whole grain includes the bran, the endosperm and the germ!
Anyway, it's just a start and just a suggestion!