RAM Configuration Guide for Best Performance

I was wondering if there is a paper that details the configuration settings that should be used to optimize RAM performance?

I'm wondering about things like the size of various caches based on number of users, the number of file handles, ulimit size or any other technical configuration parameters that could affect functionality and performance.

We discovered that the ulimit must be set high, but I haven't seen that documented anywhere.

Is there a source available for this information?

Thanks,