To join two ideas about the same person in a shorter way, you can start with the -ing form. It carries an active idea (the person is doing it) and stands for because or while. These shorter clauses sound formal and belong mostly in writing, where they pack two ideas into one neat sentence.
Start with the -ing form
Because I felt tired, I went to bed. → Feeling tired, I went to bed.
While she sat there, she read a magazine. → She sat there reading a magazine.
Because he didn't know what to say, he stayed quiet. → Not knowing what to say, he stayed quiet.
Not "Walking home, the rain started. (the rain wasn't walking)" — say "Walking home, I got caught in the rain.". The -ing part belongs to the person in the main idea, so name that person next: Walking home, I ...
Try it: Because she felt nervous, she said nothing. Make it shorter, starting with the -ing form. (Leave out the word you don't need.) Answer: Feeling nervous, she said nothing. — The shorter form starts with the -ing word and then names the person it belongs to: Feeling nervous, she said nothing. "Because she felt" is the long way you're replacing, so leave it out. The -ing part and the main idea share the same person.
Start with the past participle
When the idea is passive (something was done to the person or thing), start with the past participle instead. It stands for because or which was.
The book which was written by Orwell is a classic. → The book written by Orwell is a classic.
Because they were exhausted, they went to bed. → Exhausted, they went to bed.
Because she was surprised by the news, she said nothing. → Surprised by the news, she said nothing.
Not "The house building in 1850 is old. (it didn't build anything)" — say "The house built in 1850 is old. (someone built it)". For a passive idea, use the past participle (built), not the -ing form.
Try it: The bridge, which was damaged in the storm, is now closed. Make it shorter, starting with the past participle. (Leave out the word you don't need.) Answer: Damaged in the storm, the bridge is now closed. — The storm damaged the bridge, so the idea is passive and you start with the past participle: Damaged in the storm, the bridge is now closed. "Damaging" would mean the bridge damaged something, so leave it out. The past participle carries the passive idea.
Start with having + the past participle
When one action finishes before the next one starts, begin with having + the past participle. It shows the first action is completely over before the second, and stands for after or because.
After I had finished my work, I went home. → Having finished my work, I went home.
Because she had seen the film before, she stayed home. → Having seen the film before, she stayed home.
After they had eaten, they left. → Having eaten, they left.
Not "Finishing my work, I went home. (sounds like both at the same time)" — say "Having finished my work, I went home. (the work is done first, then I go)". Plain -ing means while / at the same time; having + past participle means earlier, already finished.
Try it: After I had finished my work, I went home. One thing happened first, then the next. Start with having + the past participle. (Leave out the word you don't need.) Answer: Having finished my work, I went home. — To show one action was completely done before the next, use having + the past participle: Having finished my work, I went home. "Finishing" alone wouldn't show it was done first, so leave it out. Having + the past participle marks the earlier, finished action.