How to write.

Three ways.

Outline.
Script format.
Mixed format.

Outline example:
-Tom enters's office building.  Drops briefcase.  Man helps but pushes into stairs.
-Tom climbs stairs.  Frank rushes by and won't answer Tom directly.
-Tom enters office and employees are in groups whispering

Script format - See Final Draft

 Mixed format example:

-TOM(65) walks into the lobby.  He drops his briefcase and the paper spills everywhere.  MAN(43) walks up and helps him gather.  Tom-"Thanks."  Man shoves the papers into Tom's briefcase.  Man-"Garten's coming down in a minute."  Tom looks at him.  Tom- "Who?"  His papers shoved into his briefcase.  Man-"Use the stairs."  Tom looks confused.  The man pushes him toward the stairs.

-In the stairs, Tom climbs.  FRANK rushes down them.  "Frank."  Frank ignores him.  Tom- "What the hell's going on?"  Frank rushes past, faintly "you don't wanna know."

-Tom's office floor.  EMPLOYEES are gathered in groups.  Whispering....