“When you don’t know what to do, just walk fast and look worried” is a work saying that has been printed on several images, including a Dilbert comic strip. Paul Dickson wrote in The Official Rules (1979):
 
“Panic Instructions for Industrial Engineers. When you don’t know what to do, walk fast and look worried. (Bob Duckles, now with the Department of Commerce, picked this up from a plant engineer who had learned it at the Ford Motor Company.)”
 
“When you don’t know what to do, walk fast and look worried” was included in a popular list called “Dilbert’s Laws of Work,” and posted on the newsgroup alt.tv.talkshows.daytime on December 13, 1996.
 
“At work, when you don’t know what to do, just walk fast and look worried” was posted on Twitter on March 23, 2011.
   
     
Google Books 
The Washingtonian
Volume 14      
1979
Pg. 155 (“The Official Rules” by Paul Dickson):
Panic Instructions for Industrial Engineers: When you don’t know what to do, walk fast and look worried. —Bob Duckles
   
2 November 1983, Chicago (IL) Tribune, “Smile,” sec. 5, pg. 1, col. 5:
Panic instructions: When you don’t know what to do, walk fast and look worried.
“The Official Rules”
   
28 November 1988, Toronto (ON) Star, “Some consider ‘work’ dirtiest 4-letter word” by George Gamester, pg. A2:
And if all else fails, just remember:

WHEN YOU DON’T KNOW WHAT TO DO, WALK FAST AND LOOK WORRIED.
   
Google Books
Good Advice
By William Safire and Leonard Safir
New York, NY: Wings Books; Avenel, NJ: Distributed by Outlet Book Co.
1992
Pg. 115:
PANIC INSTRUCTION FOR INDUSTRIAL ENGINEERS: When you don’t know what to do, walk fast and look worried. —Paul Dickson
     
Google Groups: alt.tv.talkshows.daytime
Some Jokes to brighten your day
Kathleen Austin
12/13/96
Hope you all think these are funny…...
 
DILBERT’S LAWS OF WORK
(...)
When you don’t know what to do, walk fast and look worried.
 
Google Books
Healing Through Humor
By Charles Hunter and Frances Gardner Hunter
Lake Mary, FL: Creation House
2003
Pg. 53:
Dilbert’s Rule of Order
When you don’t know what to do, walk fast and look worried.
 
Twitter
Moses Paik‏
@mosespaik
Laws of work: When you don’t know what to do, walk fast and look worried.
2:02 AM - 11 Mar 2008
 
Twitter
Quotables‏
@QuotablesLoves
When you don’t know what to do, walk fast and look worried.— Dilbert http://bit.ly/h7BuBg
2:00 PM - 11 Mar 2011
 
Twitter
BlakesFans ❤️‏
@blakefuturesfan
When you don’t know what to do, just walk fast and look worried. hahaha ...
8:00 PM - 2 Feb 2011
 
Twitter
Earl‏
@BlueMag1c
At work, when you don’t know what to do, just walk fast and look worried
3:43 PM - 23 Mar 2011
 
Twitter
J€$‏
@gildedflower
At work, when you don’t know what to do, just walk fast and look worried
3:57 PM - 23 Mar 2011
   
Twitter
Lady‏
@d_o_n_y_e_l_l_a
At work, when you don’t know what to do, just walk fast and look worried.
5:36 PM - 23 Mar 2011
 
Twitter
Men’s Humor‏
@MensHumor
At work, when you don’t know what to do, just walk fast and look worried.
7:30 AM - 9 Jul 2012
   
Funny Status
At work, when you don’t know what to do, just walk…
March 25, 2013 Work Status Updates
At work, when you don’t know what to do, just walk fast and look worried.
     
Google Books
The Official Rules:
5,427 Laws, Principles, and Axioms to Help You Cope with Crises, Deadlines, Bad Luck, Rude Behavior, Red Tape, and Attacks by Inanimate Objects
By Paul Dickson
Mineola, NY: Dover Publications, Inc.
2013 (Originally published in 1979)
Pp. 270-271:
Panic Instructions for Industrial Engineers. When you don’t know what to do, walk fast and look worried. (Bob Duckles, now with the Department of Commerce, picked this up from a plant engineer who had learned it at the Ford Motor Company.)
 
Twitter
Bill Murray‏
@BiIIMurray
At work, when you don’t know what to do, just walk fast and look worried.
2:30 PM - 14 Dec 2017