Not much to look out for really, most stuff will be under warrenty such as:
Lazy power delivery below 2.5k revs (needs an ECU remap from VW under warrenty)
Rattling front selt belt buckles - (although no cure, just poorish design)
Uneven tyre wear - points to either accident damage, poor alignment, or poor driving
Check interior for wear and tear. Leather Seats go saggy very quickly, not much can be done, but push for warrenty claim!
Check for clutch strength - floor it and see if it pulls or slips
Check under bumpers/sump for any signs of road hump damage (car is quite low)
I can honestly say, touch wood, that after 16 months and 19k miles, this car has been 99% faultless.
Whatever you do, enjoy the testdrive!