Proper vacuuming starts with a good vacuum. Of course you should consider the carpet type you have, if you have pets or not, and your budget. YouTube has many great videos demonstrating what factors make a vacuum great. After selecting your vacuum all you have to do is use it right? OK, maybe there is a little more to it.
How often you vacuum make a large difference. If you have kids and a pet, I would expect your home to have more dust and dirt settling on the carpet. In this case vacuuming more often, such as once every week or once every two weeks, is appropriate. If only you and your spouse live in the home and do not go out much, vacuuming once a month would be most appropriate.
When vacuuming, there are methods that get more debris out of the carpet vs. other ways. Consider vacuuming each area from one direction, then turn around and vacuum it from the other direction. This way the carpet fibers are brushed in more than one direction allowing the release of the most possible dirt, hair, and debris. If you have a detachable hose, vacuuming the edges of the room make a phenomenal difference. Vacuuming edges results in a much more acceptable appearance and a cleaner carpet. Because most dust hits the walls and settles on the edges of the room, you will find more dust here rather than deep dirt.
Vacuum maintenance is very important. Making sure your recovery canister or bag are empty or changed when they get full will allow you to keep picking up dirt and dust. If your brush bar is covered in hair, the agitation needed to get a good vacuuming will not be present. Verifying that each tube air passage is clear will ensure that your vacuum is working at maximum capacity.
The most important part of this information is the WHY . Why do you need to vacuum so often, in multiple directions, and keep your equipment clean? The more dirt and debris that you have in your carpet the more damage your carpet is subject to. Without care your floors will look dirty and the dirt in it will act as sand paper. Over time the grinding of debris with carpet fibers will degrade the individual fibers. This is very common in traffic areas but can be avoided with proper vacuuming as described above.
At minimum, an annual carpet cleaning is suggested. Although some people take great care of their floors, carpet cleaning will remove oils that cause dirt to stick, stains from liquids, and much more dirt than any household vacuum. If your traffic areas are worn out and looking dirty, it's far past time for a good carpet cleaning. It's called preventive maintenance for a reason. Good job getting it taken care of. Kudos to you.