What I did when I lived in Virginia was to install a piece of wood that would bear the weight of the curtains so that I could install the curtains at any height of width and not worry about studs!
The beauty of this is the wall doesn't support any of the curtain weight and the whole installation can be removed with very minimal repair to the wall.
I took a 2X4 piece of wood cut to the width I wanted the curtains to extend past the window/door, plus 3 inches.
I painted the wood on 3 sides with the same paint on my wall.
I then located the studs of the window/door frames. I located not only the side studs but the other studs above the window & door frames and marked them, too.
I transferred the location of all the studs marked with a level to the new height I wanted to install the drapes, plus 3 inches, so I could see the transferred marks.
I took the level and drew a light pencil line below where the wood would be installed. I put it below because it's just too hard to see from above when you place the wood on the wall and struggle to attach it! I found that it is best to draw a level line the entire length of the installation or do a snap-line. Otherwise, the line tends to creep up or down, even with a level...!
I positioned the wood so the rod would hang at the right height. You have to determine this by temporarily screwing your rod brackets into your piece of wood on both sides. You should have about 1 1/2 inches left on each side of the wood so it won't split. Be sure to set the brackets in the middle of the 4 inches of wood and at the correct finished width you want the curtain. Figure in how high the curtains and hooks need to be to hide the wood. You may have to use different hooks than planned to get the height to hide the wood. Be sure to adjust the height of the wood placement so the curtains will hang where you want them. Then remove the screws.
Install the wood onto the studs. Put a screw through the wood and in all the transferred stud marks. This strengthens the whole wood installation.
Screw the brackets back into the wood where you temporarily put them, and then into the wall.
Install the drapery rod into the brackets.
Install the curtains.
Erase the stud marks and touch up the paint where they were, feathering the paint out so it is not noticeable.
With 8 ft ceilings, I went just short of the crown molding minus the height of the curtain when it was properly hung with pins on the rod, about 3 inches down. That way the curtains did not interfere with the visual line of the crown molding.
The traditional height for setting a curtain is 4 inches above of the window frame. I wanted to make the rooms seem more impressive so I set the curtain height just below the crown molding.
I also extended the rods beyond the sides of the window frame so the windows appeared wider than they were. This extension on the sides had the added benefit of allowing me to push the curtains back as far as possible while still hiding the side window frames. That allowed the fullest amount of light possible to enter each room. Since the house was an interior townhouse, this was a huge benefit and lightened up the entire house.