The sad truth is that most professional carpet cleaners and oriental rug cleaners just do not know how to properly pre-spot clean areas. Over and over we hear about so called professionals who carry in only one spotter bottle even though there are multiple spots.
The fact is, each different type of spot often requires completely different chemicals to clean effectively. Some spots require high pH while others requires something more acidic. Coffee and tea are best cleaned with tannin removing agents, while rust requires an entirely different approach.
Of course, its still best to let your cleaner know on the phone about any particular spots you are worried about on the phone ahead of time so they can make sure they have the right chemicals on their truck to do the job right.