Rods are a simple and cheap way to keep curtains where the belong--covering your windows. There are many strategies for securing a rod so that it does not sag in the middle and make your curtains bunch up. With a few extra minutes and some simple parts and tools, you can find a foolproof way to keep your curtain rods straight and true.
The simplest solution is to use a pre-fabricated bracket. Curtain rod brackets are A-shaped, with the narrow end curved to allow the rod to sit on top of it. Simply screw the bracket to the wall (to a stud, if possible) and put the rod on the bracket's dimple.
You can secure the rod from above by using a line of some sort--steel wire or cloth, depending on your decor. Install a bracket or hook above the center of the rod, on the wall or on the ceiling, and connect it to the rod. Tension the line enough so that the line supports much of the weight of the curtains. One simple and stealthy design: Use a small eye screw in the ceiling and use fish line to tie the rod to the screw for a decent solution that is hard to see.
Buy decorative molding that will give you a place on which to rest the rod or pass it through. An ornate centerpiece to a window's trim not only looks elegant, but it can provide the hardware you need to solve your curtain rod problem. Install the molding and put it on or through the molding piece, then thread the curtains in from the side. It may be necessary to install a discrete screw to keep the rod in place.