There is just a touch bit of science that goes into freshing up your carpet, however it doesn't have to be expensive, difficult, or painful. You can choose a wide range of products. And you really do have options.
It is a good idea to start by vacuuming the area really well. Carpet tries to old the dirt in so the better your vacuum is at sucking that dirt out, the cleaner your carpet will be.
It is a good idea to invest in an inexpensive carpet cleaner. I highly recommend Bissell's QuickSteamer. It costs about $50 and will get dirt out of even the cleanest looking carpet. For really fresh carpet clean regularly after vacuuming. This should be done before going to bed for the night to give the carpet time to dry. It will help take up pet odors, stains, and deep down dirt. You can also buy specific cleaners to meet your need such as a pet odors cleaner or other item.
Pet odor spray
A good portion of our household smells come from organic materials in our carpet. It could be pet dander, pet accidents, spills, and even materials brought in on your shoes. The easiest way to get rid of these smells is to buy a pet odor eliminator. Most of these sprays work with enzymes that consume the bacteria and the matter that is causing it. Even if you don't have pets, these sprays can make for a much fresher home. You will want to check and make sure that they do indeed contain enzymes and then simply spray lightly over your carpet (and furniture if you wish). It won't take long and you should notice a difference very quickly. Plus this is a natural way to eliminate odors and to freshen the carpets.
Baking soda is a natural way to freshen the carpet as well. It kills bacteria and absorbs odors. However, you need a good vacuum cleaner to suck it all up or else it will just remain behind in your carpet, trapping odors, and adding to the build up in your carpet. If you do indeed have a good vacuum then lightly sprinkle the baking soda over the carpet and leave for about a half an hour. Then vacuum it up and enjoy fresher carpets. Want something all natural that freshens and adds a nice smell? You can mix a few drops of essence oils in with your baking soda. This needs to be done a few times and then it should be run through a sieve or stirred really well with a fork. You can also do the same thing with powdered cinnamon for a lovely scent. You can choose scents for their anti-bacterial benefits such as chamomile, or for their aromatherapy benefits such as lavender.
Fresh all natural carpet spray.
You can also make a fresh carpet spray. You will need a spritz bottle. Add 3/4 water, 1/4 vodka or Ever Clear (or another white high alcohol content liquor), and then 10 drops of the essence oil of your choice. Shake generously before each use. Spray your carpets lightly. At first they will smell of alcohol, but as they dry the odors will be eliminated, bacteria killed, and the fragrance of the essence oil left behind.
While not all natural, Fabreeze and similar products can and do leave for fresh smelling carpets. You can generously spritz down the room and its carpet right before bed and wake up to a fresh smelling carpet that is dry and ready for company.
However you decide to treat your carpet, with just a touch of work you can have fresh smelling and actually fresh carpets. It doesn't have to be really expensive and maintaining a good carpet doesn't have to be a difficult process. just a little work and you will have the freshest, company ready carpet in town.