Using a present or past participle.

we can use -ing & -ed forms:
a) combined with other words to make participle clauses.
e.g., Not  knowing where she was, I rang her on the  phone.
(=Because I didn't know where she was, I rang her on the cell phone.)
Left waiting in the rain for an hour, he felt very angry.
(=He  had been left waiting in the rain  for an hour, so he felt very angry.)

b) after nouns to make reduced relative clauses.
e.g., Can you see the man sitting on the bench?
(=Can you see the man sitting on the bench?)
We drove past treets blown down by the storm.
(=We drove past treets that had been blown  down by the storm.)

c) after conjunctions and prepositions.
e.g., After eating dinner, I like to take a long bath.
When traveling, I like to take a dairy with me.