The basics are:

Latest video card drivers
Latest motherboard drivers
Latest soundcard drivers
Latest directX version
Check your case temps

It looks like the support page you need is here:
http://techsupport.rockstargames.com...&submit=Submit

but the only patch they offer is unrelated. And dude, the 3rd party patches for that game look so fun I'd consider buying it even though I played the PS2 version.