Here are the Best Practices and Troubleshooting articles which are related to GUP.
Group Update Provider: Sizing and Scaling Guidelines
http://www.symantec.com/business/support/index?page=content&id=TECH95353
Best Practices with Symantec Endpoint Protection (SEP) Group Update Providers (GUP)
http://www.symantec.com/business/support/index?page=content&id=TECH93813
Configuring the Group Update Provider (GUP) in Symantec Endpoint Protection 11.0 RU5
http://www.symantec.com/business/support/index?page=content&id=TECH96419&locale=en_US
Guide to create the GUP for remote location
https://www-secure.symantec.com/connect/downloads/create-gup-symantec-can-help-conserve-bandwidth-clients-remote-location
How to Setup a Group Update Provider (GUP)
http://www.symantec.com/business/support/index?page=content&id=TECH105005&locale=en_US
Tips For Installing SEP In A Low Bandwidth Environment
https://www-secure.symantec.com/connect/articles/tips-installing-sep-low-bandwidth-environment
Symantec Endpoint Protection (SEP) Group Update Providers (GUPs) Selection
https://www.symantec.com/business/support/index?page=content&id=TECH198702
Troubleshooting the Group Update Provider (GUP) in Symantec Endpoint Protection (SEP)
http://www.symantec.com/docs/TECH104539
How can we check which content SEP 12.1 clients are downloading from GUP?
https://www-secure.symantec.com/connect/articles/how-can-we-check-which-content-sep-121-clients-are-downloading-gup
How to confirm if SEP Clients are receiving LiveUpdate content from Group Update Providers (GUPs)
http://www.symantec.com/business/support/index?page=content&id=TECH97190
SEP Content Distribution Monitor (for GUP health-checking)
https://www-secure.symantec.com/connect/downloads/sep-content-distribution-monitor
How to analyze Debug logs from GUP to determine which clients are taking definitions from GUP
https://www-secure.symantec.com/connect/articles/how-analyze-debug-logs-gup-determine-which-clients-are-taking-definitions-gup
Video’s created on Group Update Provider on the Symantec Connect website.
https://www-secure.symantec.com/connect/videos/group-update-providers-part-1
https://www-secure.symantec.com/connect/videos/group-update-providers-part-2
GUP content monitoring tool video
https://www-secure.symantec.com/connect/videos/sep-content-distribution-monitor-introduction
Hope it can help to all.
Thanks
Sumit G.