Use a comma:
· After an introductory word.
Quietly, she tiptoed past the sleeping child.
Haltingly, the soldier called out, “Who goes there?”
· After an introductory phrase
Running slowly, Ed finished a marathon in five and a half hours.
Being frank, Tom said, “I’m not myself, today.”
· After an introductory clause
After she wrote a chapter, she went out for a run.
When Tom heard the doorbell, he chimed in, “There’s someone at the front door.”
(Love those Tom Swifties)