Gerunds after Prepositions

This is a good rule. It has no exceptions!
If we want to use a verb after a preposition, it must be a gerund. It is impossible to use an infinitive after a preposition. So for example, we say:
I will call you after arriving at the office.
Please have a drink before leaving.
I am looking forward to meeting you.
Do you object to working late?
Tara always dreams about going on holiday.
Notice that you could replace all the above gerunds with "real" nouns:
I will call you after my arrival at the office.
Please have a drink before your departure.
I am looking forward to our lunch.
Do you object to this job?
Tara always dreams about holidays.
The above rule has no exceptions! So in the following examples why is "to" followed by "driving" in the first and by "drive" in the second?
I am used to driving on the left.
I used to drive on the left.
Show answer

When we have two verbs together in a sentence, the form of the second verb is influenced by the first verb.

This table shows which verbs require the second verb to take the form of the bare infinitive (infinitive without to).

Verb + bare infinitive
The bare infinitive (an infinitive without 'to') is used after certain verbs which are followed by an object: let, make, see, hear, feel.	My parents didn't let me watch TV at night. Did you see anyone enter the building? He made me laugh.
The bare infinitive is used after modal verbs:can, should, could, might, may, etc.	He can't sing. It might be a good idea.