Protein first as a general rule, in order that the stomach "sees" how much HCl and other proteases to let go. As protein nearly always comes with fat, they can be taken together.
Carbs in *significant amounts* taken away from protein meals, as they require completely different pHs to digest properly. Note that in Paleo foods, carbs nearly always appear by themselves within the same food. Protein and fats show up together in meat, nuts, and seeds.
That's the basics.