carpets' types can be wool,synthetics,oriental,according to the carpet material,the suitable cleaning solution is used.

Carpet is everywhere! People who understand carpet know that its immense success and consumer acceptance is not due to chance. Few construction materials offer the advantages that carpet does. Carpet is colorful, comfortable and yet easy to maintain. Even though it appears expensive, it is often the most economical choice for floor covering. Carpet and rugs found on the floors of residences and commercial buildings still represent a substantial investment. In light of this, is it not wise to maintain them correctly?

Like all textile materials, the beauty and life of a carpet depends largely on the care that it is given. Proper maintenance can add years of attractive life. Specific maintenance procedures for carpet are determined by where the carpet is installed. In general, proper maintenance involves regular vacuuming and periodic cleaning by methods such as hot water extraction, shampooing, bonnet cleaning, foam cleaning, etc.

Regular vacuuming is essential as it removes particulate soil that damages the fibers. Vacuuming maintains the surface appearance of a carpet and keeps the level of soil in the pile at an acceptable level. Vacuuming should be done at least once every two weeks, preferably once each week and even twice per week in soiled or heavily trafficked areas. It is important to use a well-maintained, good quality vacuum. Vacuuming removes only particulate soil and surface dirt; therefore, other methods of cleaning are periodically required to improve the appearance of the carpet. Wet cleaning methods are better for removing oils, greases and other forms of matter that cause soiling on carpet. These methods are mostly used by professional cleaners and trained personnel, but smaller, less powerful units, can also be rented for use by customers.

It has been said that ignorance is bliss. Sometimes, maybe, but not always. Before having a carpet cleaned, you may find it helpful to understand some of the carpet cleaning methods. The best method for cleaning a particular carpet is dependent on a range of factors. All carpet cleaning methods offer various advantages, but also have some limitations. No single method is superior to all others. Properly performed under appropriate conditions, each method can provide satisfactory results. Often, several methods can be combined to achieve the desired results. The following are some of the more prevalent carpet cleaning methods.

Don't rub in blot liquids!

Use a clean white cotton cloth or plain white paper towels. Once you have removed the liquid, rinse the spot with water and blot again until dry. Repeat if necessary to remove more of the stain, but don't scrub the area, or you may damage the carpet and set the stain in more permanently.

I just saw this site. It has an amazing list of stains and ways to remove them...

Carpet Stain Index and Guide
http://www.fabriclink.com/stains/Carpet.cfm

Hope this helps!

Wow, that is a great list! Although if nothing seems to be working, Id consult a professional carpet cleaner, such as the consultants at ChemDry.