First thing is to make sure all the hardware is 10/100/1000 (gigabit) speed
rated. That means the LAN adapters, the router(s), any switches, and
especially the cabling and connectors. After that, it's all relatively
*quite* minor advantages perhaps gained by tweaking, which I don't bother to
do.
http://www.google.com/search?hl=en&q=10/100/1000+cabling
Note that no matter how good the shielding and quality of the cable, it's
still going to pick up noise if it's "loud" enough and close enough. "Noise"
is derived from electric devices, like a blender, or CRT monitor, or the
computer itself, or even if it runs too close to household interior
electrical wiring, even the high-tension grid running behind your back yard.
Things like that. But once you have the correct and at least decent quality
hardware installed, the rest usually amounts to minor variations.