Three-quarter inch diameter is an excellent option for standard and double windows. The three-quarter Iron Art by Orion Collection is perfect because it's large enough to appear substantial on small windows, but not so large that it overwhelms. Use with grommet, tab-top or rod pocket draperies and valances. Or, choose a coordinating ring for pinch-pleat.
Square shaped curtain rods are a really popular option. And, both regular and hammered square rods are available with this collection. For a modern style, the regular version would probably be the best option. Finished in while, black or pewter, they'll provide a sleek contemporary feel to your treatment. The hammered version is great for a rustic and traditional appearance. Paired with a classic finish, the indentations create a nice weathered look.
Corner installations are really easy if you use a fixed elbow. You can create a perfect ninety degree bend by using two pole sections with the elbow. It's important to remember to install support brackets just before and just after the elbow because the elbow itself doesn't provide additional stability to the rod. It just continues the look of the pole around the corner. Without the correct number of brackets, the curtain rod might fall down. And, keep in mind that if you're using a drapery with rings, the curtain won't be able to move past the elbow.