Curtains generally look best if they are hung high and wide. Stock sizes of curtains are usually 84" or 95" long. Measure up from the floor to figure out where 84 will land in relation to your window. If 84 is too short, you'll have to use 95. 95 might be a little cramped by the ceiling but they will look better than panels that are too short.

If you are crafty, you could hem the 95s or add some fabric to the 84s.

Make sure your curtains appear wide enough to cover the windows even if you don't plan on closing them. You don't want them to look too skimpy.

Here is a good graphic about curtains. I like all the advice except the pooling suggestion.

I agree with d_gw.

Also give some thought to whether you might decide at some point to add crown molding to the ceiling.