Does the window open up, slide (think French doors) or crank out? Are they deeply set-in windows or flush with the wall? These are important facts to know when you go shopping...not every blind will apply to every style of window.
Do you have windows that meet at a corner? Then look for vertical blinds rather than horizontal blinds. Horizontal blinds will interfere with each other at the inside corner as you raise and lower or tilt them. Vertical blinds will avoid this problem.
How do the windows open? If they crank inward, make sure the blinds are long enough or wide enough and are mounted high or wide enough so that the windows can open unimpeded when the blinds are drawn.
Do you want the option of lowering the shade from the top rather than raising the shade from the bottom? This option is available with some blinds and allow maximum light with maximum privacy.