1. Reducing Adverb Clauses:
Adverb clauses can be reduced to adverb phrases, just as adj clauses can be reduced to adj phrases.
Omit the subject of the dependent clause and the be form of the verb:
While I was walking to class, I fell down.
While walking to class, I fell down.
If there is no be form of the verb, omit the subject and change the verb to –ing:
Before I left for work, I took a shower.
Before leaving for work, I took a shower.

2. Reducing Adverb Clauses:
An adv clause can ONLY be reduced if the subject in both clauses is the same:
While she was driving to work, Ann got a call from her boss.
While driving to work, Ann got a call from her boss.
But NOT: While driving to work, her boss called her.

3. Time clauses:
Adverb clauses beginning with after, before, while and since can all be reduced. The adverbial phrase can also come after the main clause:
Peter went to bed after finishing his homework.
During the same time:
Sometimes while can be omitted at the beginning of the sentence:
While I was walking to work, I saw Mary.
While walking to work, I saw Mary.
Walking to work, I saw Mary.
Adverb clauses beginning with when can begin with upon +ing when they are reduced:
When I turned 21, I got married.
Upon turning 21, I got married.
On turning 21, I got married.

4. Cause and Effect:
When you reduce an adv clause with because, since or as, don’t include because in the adverbial phrase:
Because she needed help, Jan called her brother.
Needing help, Jan called her brother.
Having + past participle gives the meaning of because and before:
Having seen the movie, I don’t want to go again.

5. Practice with making adverb/adverbial phrases
When the team won the game, they celebrated their victory.
Upon winning the game, the team celebrated their victory.
While I was talking to my friend, I suddenly realized I had an appointment somewhere else.
While talking to my friend, I suddenly realized I had an appointment somewhere else.
The students did really well on the test because they had studied for it.
The students did really well on the test, having studied for it.
Before we leave for the party, let’s clean the house.
Before leaving for the party, let’s clean the house.
John sat in his room and thought about his future.
Sitting in his room, John thought about his future.

6. Some more adverbial phrases:
With “by” plus present participle: shows method or way to accomplish something
By attaching the wire to the battery, we were able to complete the circuit.
With a past participle: used for passive meaning.
Presented with the choice of marrying the ugly, rich man or her poor lover, Josephine chose __________.