Here are two tips to follow if you want to maximise the results of using carpet cleaning services.
Show them which areas of any dark or patterned carpets have stains or are smelly
If you have very dirty carpets that are dark-coloured or have a busy pattern, you should indicate to the cleaner which areas of these carpets have stubborn stains you've been unable to remove yourself or which sections are the most malodorous. The reason for this is that if the carpets are dark or patterned, then the cleaner might have a hard time locating the stained parts. Likewise, whilst you might notice the smell coming from a particular spot on a carpet, the cleaner might not detect this odour when they walk by.
By showing them these particularly dirty areas at the start of the carpet cleaning, they can pay special attention to these spots to ensure that any stains are fully removed and any odours are eliminated. They might, for example, choose to pre-treat these areas and let these pre-treatments tackle the worst of the stains and odours whilst they steam-clean some of your other carpets before they then steam-clean these spots. Additionally, they might decide to go over these areas with their steam cleaner several times to ensure they are pristine.
Stack the furniture that has to remain in the rooms whose carpets are being cleaned
If you are prepping the area but have some furniture that you can't take out of a room, try to stack it on top of other furniture. For example, you may want to put your coffee table on the sofa and your dining chairs on the dining table (with the chairs' seats resting on the tabletop so the legs don't scratch this surface).
This will maximise the amount of floor space that the cleaner can access and wash. It will also mean that they won't have to waste any of the cleaning session working out how to balance certain furniture items on other pieces of furniture. Further, it will reduce the number of furniture items they have to move around in these rooms when washing the carpets (as instead of, for example, having to move the dining table and a few chairs, they'll only have to drag the table). This, too, will increase the time they get to spend focusing on the carpet cleaning.
Contact a carpet cleaning service for further information.