How To Optimise Controller Execution Time

Hi All,
Im trying to improve performance of an ap I created and at the moment looking into how best to improve Controller Execution Time.
I know the first thing would be to make sure Im not auto loading any libraries etc that are not relevant.
I also read that not posting the .php extension when calling a view file might help. Whats anyones view on that ? How would that help and if it does how much an improvement might we see.
Most page load up in less that 0.5
I would love to hear your tips and advice.