When carpets have been steam cleaned properly they should not be extremely wet, but it is recommended that you keep off them as long a possible before walking on them. If you can wait overnight till the next day this is ideal but if the place is well aired they should be fairly dry within 6 hours.
A professional carpet cleaner can provide a range of products and ways to bring your carpets back to life. Removing the embedded dirt and dust can also help those who suffer from allergy issues.
Not all carpet stains are able to be removed. It depends what the stain is caused from and how long it has been there.
It is recommended to give the carpet a vacuum before you have steam cleaning done. Many companies offer this before they clean, sometimes at an additional cost.
The most commonly seen is Penguin Steam Carpet Cleaning where hot water is pushed into the carpet then extracted back out to remove dirt and clean the carpets.