The areas of heat gain that you can control:
Internal gains - switch to CFL's, shut off electronics if possible.
Windows - shade or solar screen. Sure the screens help on the East and West sides of the house. If your window are not low-e, then they help even more. If you already have pretty low SHGC windows, then you are not going to gain much.
Infiltration - If you are handy, then you can usually cut this down enough to make a big difference. The easiest place to make a difference is in an attic with blown insulation. You push the insulation aside and look for penetrations of wire, plumbing etc. Then you either foam or caulk around these areas. There is more to it when you have recessed cans but the info is available.
Wall-ceilings - really not much easy to do here except add attic insulation. This is probably not going to help much although it will help. It all depends where you are starting. If you have r-30, then going to r-40 is not going to help that much.

Find a window in direct sun. Open the window and put your hand in front of the window and compare to no glass blocking the sun.

If the heat is about the same, then you don't have low-e windows. The hand behind the glass should be much much cooler. There are differences between low-e windows and the quanitative assessment is the SHGC - solar heat gain coefficient. A good window for the South is .3 or less.

In NC, you can still build a house today without low-e windows. I think very few actually do. Either way - your house could have either but it certainly depends on your location.