Problems with prepositions

Rule 1

You may end a sentence with a preposition. Just do not use extra prepositions when the meaning is clear without them.

That is something I cannot agree with.

How many of you can I count on?

Where did he go (to)?

Where did you get this (at)?

I will go later (on).

Take your shoes off (of) the bed.

You may not look out (of) the window.

Cut it (up) into small pieces.

Rule 2

Use on with expressions that indicate the time of an occurrence.

He was born on 23 December.
We will arrive on the fourth.

Rule 3

0f should never be used in place of have.

I should have done it.

I should of done it.

Rule 4

Between refers to two. Among is used for three or more.

Divide the money between the two of you.
Divide the money among the three of you.

Rule 5

Into implies entrance, in does not.

Sally walked into the office.
Sally was waiting in the office.
Cut the cake into six slices. (The knife enters the cake.)