Appropriate preposition use is frequently idiomatic; however, these are general guidelines for choosing the correct preposition:

1. Prepositions indicating time & date: at, on, by, before, in

Idiomatic:

• specific hour on the clock uses at: at 7:00
• specific day or date uses on: on Thursday
• specific month or year uses in: in July or in 1999

2. Prepositions indicating time: to, from, since, for, during, after

3. Prepositions indicating travel & movement: from, to, at, in by, on, into, out, out of

4. Prespositions indicating position: above, below, over, under, beneath, on, in

In addition to these general guidelines, some verbs require particular prepositions.

Finally, some modifiers also require particular prepositions. To determine which preposition is appropriate, consult a dictionary. Any good dictionary will indicate the particular prepositions required by specific adjectives.