Normally I can tell by just looking at the steering wheel, gearstick, pedals etc. They will often tell straight away if it has been used a lot. I'm sure more experienced mechanics will be better able to spot a lemon using their own methods. It might be an idea to bring one along
However, this particular jeep has 28k on the clock. It's a 2004 commercial. According to the log-book it's had 1 owner from new and the last DOE (May 2006) recorded the mileage at 20k. If it was clocked, it was clocked by the owner maybe a year and a half into ownership (i.e. pre DOE test in May '06) and not the garage, which seems unlikely.
The only thing throwing me is that the service booklet looks brand new! Not a crease on any page, and there's nothing in it, not even a pre-delivery inspection stamp. Perhaps it was lost and replaced, I can't remember what the salesman said at the time, but I'm just trying to cover as much as I can.
Having said all that, the inside is spotless (seats, dash, carpets etc) and the bodywork is very good which leads me to think the mileage is genuine. The garage are also giving a 12 months Toyota Dealer Cover warranty on it, which should stand for a lot.