You can usually tell a well loved example on generally the condition, how clean it is i.e. has it been given a quick going over with a grubby sponge or is the car generally well cared for - all spokes on the wheels cleaned, wheel arches clean, door sills etc. That's a good start in telling how it's been cared for and might give you some indication on its overall health.
Look at the service history, is it complete, check when the car was serviced and the gaps between the services. How is the service history presented? All in a tidy wallet or is it all just scrunched up and stuffed into an envelope. All small things but they add up..
Start the car from cold, is there any hesitation, is the idle rough and lumpy? When you drive it, does it make any strange noises, does the engine rev freely etc. When you look at the engine, is the engine bay generally clean? Are there splatters of anything under the hood that look suspicious? Common sense stuff really.
I'm afraid I have no experience with using RAC or AA checks. Do you know of anyone who is 'car minded' that might be able to come along with you?
I'm sure others may have used an independent check or mechanic and will be able to advise.