I had to troubleshoot the performance on one of my MySQL installations. Being a while since I did some MySQL performance tuning, I thought it would be a nice time to document the info in my blog.
To find how may users/threads/sessions are connected, at the MySQL prompt type: show processlist. To find if the cache hit ratio is good, or if memory is allocated properly, or if index seeks for read/writes are effective: show status. To find index health: show index.Use the \G switch at the end of the statement to group the output rather than having the default tabular output.
The detailed syntax with explanations of columns can be found from the MySQL documentation here.