Incorrect: We have been playing since two hours.
Correct: We have been playing for two hours.
Use since with the starting point of action; use for to indicate duration.
Incorrect: This table is made with mahogany wood.
Correct: This table is made of mahogany wood.
We use made of when we identify the material used to make something.
Incorrect: Paper is made of wood.
Correct: Paper is made from wood.
When the process of manufacture changes a material into something completely different, we use made from.
Incorrect: He came to meet me in 5 o’clock.
Correct: He came to meet me at 5 o’clock.
We use at with clock times.
Incorrect: She married with a friend of her brother’s.
Correct: She married a friend of her brother’s.
The verb marry is usually followed by a direct object without a preposition.
Incorrect: It is Susan at the phone.
Correct: It is Susan on the phone.
The correct expressions are: on the phone, on the radio, on TV etc.
Incorrect: It is imperative that the meeting start in time.
Correct: It is imperative that the meeting start on time.
‘On time’ means ‘at the planned time’. When something happens on time, it is neither late nor early. In time means ‘before the last moment’.
Incorrect: I will never forget meeting him on that afternoon.
Correct: I will never forget meeting him that afternoon.
Prepositions are not used in common expressions of time beginning next, last, this, that, one, each, every, some, any, all.