
The last time I hung curtain rods, it involved a ruler, a level, a pencil, a drill, and the hardware, and the end result was a little wonky. It's hard to hold all that stuff, especially when you're perched on a ladder. But one piece of stiff cardboard can make the process simpler and faster.
Miss Mustard Seed's solution utilized a template with chipboard or sturdy cardboard.
First, she cut a three-inch square from the corner of the board (to put over the window frame corner). She had already decided how far out and up she wanted her curtains to hang to make them "high and wide," and she measured seven inches up and nine inches out on the template. She used the curtain rod's bracket to mark the screw holes with a pencil, then drilled through the template, and flipped it over to use it on the other side of the window!
Read More: Hanging a Curtain Rod (Made Simple) at Miss Mustard Seed
Image: Miss Mustard Seed

Nomade Express Slee...
Just make sure your window itself is straight before doing this, otherwise you'll end up with a horribly crooked curtainrod. When I was installing my new curtainrod I measured off of my windows. Once everything was in place the right side was a few inches higher than the left! I found that I have to measure down from my ceiling instead. Thankfully my curtains hide the extra holes.
I once purchase a set of curtain rods that included a notched, pre-"drilled" cardboard template to place the brackets (just like this example)... I've saved it ever since! Best idea ever. I'm considering converting it to a piece of wood w/a variety of layouts/rod placements for future moves.
Good idea!