1) Should I select the central AF point or use auto? Yes, unless you focus on one spot of the track then like fearlesspierre thats how i shot this shot
2) Should I switch off the IS on the lens? yes, its is not a help with moving objects as MBrutus2009 said.
3) Should I use AI focus or AI servo for the AF mode? AI servo is a must for tracking a moving motorcycle, i also prefocus with AI servo
4) Should I use Evaluative, Partial or Centre-Weighted ave Metering? metering is still something i have yet to mess around with on my 40D but it really depends on what your aiming for. i usually use the EV +/- to adjust for what i think the pictures could use.
when you shoot at 1/50th are you trying for something like this?
if you want clear results you should shoot much faster
check out my post for more photo's like these: http://www.cameralabs.com/forum/viewtopic.php?t=10922