Recommended advance settings

Hi
Was wondering if anyone could advise which are the best settings for the advance wireless setup or are the defaulted values best?
Have read that to improve wireless we can set beacon interval at 50, RTS threshold at 3406, Preamble short instead of long etc.
Also, would like advice on whether multicast broadcast should be enabled or not.

I have been having intermittent lag on the internet on my notebooks via wireless although this has improve since my previous post.. had to insert the primary and secondary dns servers (google) instead of automatic cos I think my local ISPs dns servers may be swamped...

Thanks