what is the best approach to run splunk queries
Start here - it shows the basics https://www.splunk.com/en_us/blog/customers/splunk-clara-fication-search-best-practices.html Here are all the many different commands with SPL with examples - once you have developed the basic concepts, you can start to apply various commands for your use cases.
https://docs.splunk.com/Documentation/SplunkCloud/9.1.2312/SearchReference/ListOfSearchCommands
