when to use on, in, and at when writing english?

Answer 1

in, at, on can be prepositions of location or time. the site below will explain them when used for location.
the rules for time are pretty simple with few execptions: in a year, month, eg in 1995, in september; on a day eg on monday, on christmas, on weekends; at a time eg at 9am, at lunch time. i hope this helps you.

Answer 2

Gosh, there is no one rule, for sure. Depends on the contects. Try to remember what you read and hear - and all will gradually become easier...

Answer 3

Dont' ever use them at the end of a sentence, for starters!