There is a large number of different digital clocks on the market. Knowing how to set a particular make and model can be a real problem.
The following links to videos and manuals may be helpful.
Reviews of clocks can be found here.
Clock Manuals
Clock Setting Videos
DGT 3000
Setting (long)
Setting (brief)
DGT 2010
Setting (mode 21)
DGT XL
Programming
DGT Easy Plus
Setting
DGT 1001
English Chess Company Timer (Leap)
Setting 1
Saitek Competition
Saitek Competition Pro
Saitek Pro III
Chronos
Chronos II
Chronos GX
Garde
Example Setting 1
Example Setting 2