Always check the timing belt has been done on time (costs around $770 at Alpine Affaire in Ringwood, VIC), and check for any evidence of wear on gearbox and engine mounts. You can tell if the mounts are failing sometimes due to excessive vibration at idle. Honestly, best bet is to do what I did and pay a specialist workshop an hour labour to do a mechanical inspection (a RWC only says it is safe to drive, not that it is in good condition). I got a compression test, all mounts checked out, full underbody check for chassis repair or damage, and suspension check. Only cost me $105 which was so worth it for the peace of mind. Other typical issues are driver's window, wear on the recaro seat bolsters and seat rails, and cheap tyres being put on to pass RWC. Mine have heaps of tread (Toyo Proxes T1 Sports) but can't put power down in 3rd gear unless the road is dead flat and dry. I'm looking at at least a $1,500 bill to upgrade to Pilot Sport 3s or Pilot Super Sports, so bear that cost in mind!