Microsoft has release a poster highlighting some of the key health indicators (KHI) to be used in conjunction with the script inside of the Lync Server Networking guide. Of course, it has to be said that this isn’t the sum total of everything you’ll need to monitor, and remember that there are a lot of components outside of Microsoft Lync that you’ll need to monitor as well (heavy networking and SBC monitoring is a must). However, this is extremely handy and I urge everyone to take a look!
Link to the KHI poster: http://www.microsoft.com/en-us/download/details.aspx?id=41697
Link to the Lync Server Networking Guide: http://www.microsoft.com/en-us/download/details.aspx?id=39084