Fortunately Lync has some really good tools that help analyse issues if they are repeatable and help determine what to do to fix the issue.
Here is a list of training resources that should help you.
Webcast - Troubleshooting Microsoft Lync Server 2010
Troubleshooting Microsoft Lync Server 2010 Clients: Help Desk Resource
Microsoft Lync Server 2010 Resource Kit Tool: Snooper
Troubleshooting Lync Server 2010 with Snooper: Part 1
Troubleshooting Lync Server 2010 with Snooper: Part 2
Troubleshooting Lync Server 2010 with Snooper: Part 3
Troubleshooting Lync Server 2010 with Snooper: Part 4http://blogs.technet.com/b/nexthop/archive/2012/05/07/troubleshooting-lync-server-2010-with-snooper-part-4.aspx
Apart from these I can also say that I rely heavily on the blogs and forums for the various Lync and UC MVPs and Masters out there.
People like Jeff Schertz, Matthew Landis, Tim Harrington and Elan Shudnow to name a few. Thanks guys.
I hope these help.