So your painting your house exterior and you accidentally smeared acrylic latex paint on the windows. What is the best way to get it off?
If you happen to be one of the unlucky folks to be in this situation, fear not, the best thing to do is nothing until the paint has thoroughly dried.

If you panic and try to clean off the paint while it is still wet, you will do more damage in the end. Smudging the paint will create an ultra-thin layer that later becomes almost impossible to remove.
As counter-intuitive as it seems, the more paint glopped onto the surface, the better.
After you let the paint rest for several hours, begin working the edge with your fingernail. The entire glob should peel off in one piece, leaving no trace. This will work whether on the vinyl frame or the glass.
If you happen to have smaller specks on the glass, carefully use a razor blade to get it off.