Things that Give Writers Fits
Prepositions
The very subtle differences in the meaning of to, on, in, by, for, and at cause many people big fits. I don’t know what to tell you about this problem except that, well, you’re just going to have to memorize the differences. Don’t worry too much, though. Most people new to English usually pick up these automatically within a few years.
I wish English wasn’t so darn complicated.