What is the best training material you've seen to help you move towards a clustered environment?
try this link to create instance test environment
https://github.com/mhassan2/splunk-n-box
Lab docs I wrote to train consultants?! 🙂
Seriously though, this high-level topic in the docs should get you started. Clustering Deployment Overview. If you have specific questions, the docs feature a feedback link, or you could ask the question here.
I used http://docs.splunk.com/Documentation/Splunk/6.5.0/Indexer/Aboutindexesandindexers
both for Indexers and Search Head Clusters.
Bye.
Giuseppe