Backup and Recovery Best Practices for Backup Vendors - credit to Jeff Hunter

IBM Tivoli Storage Manager (TSM):

https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/Tivoli%20Storage%20Manager/page/Tivoli%20Storage%20Manager%20for%20Virtual%20Environments

EMC Avamar:

http://www.vce.com/asset/documents/avamar-data-domain-whitepaper.pdf

A VCE document, many of the best practices will apply regardless of platform.

Symantec NetBackup:

http://www.symantec.com/docs/HOWTO70892

CommVault Simpana:

http://documentation.commvault.com/commvault/v10/article?p=products/vs_vmware/best_practices.htm

http://documentation.commvault.com/commvault/v10/article?p=white_paper/virtualization/vmware_building_block.htm

VMware KB - Best practices when using advanced transport for backup and restore:

http://kb.vmware.com/kb/1035096

VMware VDDK:

https://www.vmware.com/support/developer/vddk/

Contains some interesting info on how the APIs work and how backup vendors can utilize them, which may be of interest to partners and customers.

VDDK Tips and Best Practices:

http://pubs.vmware.com/vsphere-55/topic/com.vmware.vddk.pg.doc/vddkBkupVadp.9.5.html

General tips:

Agent-less backups are fine for the majority of VMs. A few VMs, however, do benefit from using agent-based backup and recovery. Examples include applications like SQL Server and Exchange, which often require log management. Another example is VMs that generate very high levels of i/o, which sometimes cause issues with VM snapshot creation and consolidation.

In some cases, using the SAN transport for performing backups may be beneficial. However, this typically requires use of one or more physical machines that serve as a proxy or data mover. A quick search on Google - backup san transport - will provide details on this technology and who supports it.