adverbs
in the historical present; at this point in the narration of a series of past events
"President Kennedy now calls in the National Guard"; "Washington now decides to cross the Delaware"; "the ship is now listing to port"
in these times
"it is solely by their language that the upper classes nowadays are distinguished"- Nancy Mitford; "we now rarely see horse-drawn vehicles on city streets"; "today almost every home has television"
used to preface a command or reproof or request
"now hear this!"; "now pay attention"
at the present moment
"goods now on sale"; "the now-aging dictator"; "they are now abroad"; "he is busy at present writing a new novel"; "it could happen any time now"
without delay or hesitation; with no time intervening
"he answered immediately"; "found an answer straightaway"; "an official accused of dishonesty should be suspended forthwith"; "Come here now!"
(prefatory or transitional) indicates a change of subject or activity
"Now the next problem is..."
in the immediate past
"told me just now"