Look for powerful suction and good scrub brushes for the best home carpet cleaners. These are the two factors that determine how effective a home carpet cleaner will be.
Buy a home carpet cleaner with a large water tank to reduce the number of times you have to stop and refill the tank. This will reduce the amount of time it takes to clean the carpet. Conversely, be aware that a big water tanks means a heavier home carpet cleaner. If you are especially petite, the best home carpet cleaners might be the ones with a smaller water tank.
Compare the accessories on home carpet cleaners and consider what you need in terms of cleaner functionality. Some carpet cleaners have furniture attachments which will come in handy for homes with pets or for cleaning carpet on stairs. One big difference between carpet cleaner features is some heat water and some don't.(This is why it's a misnomer to call home carpet cleaners, steam cleaners, not all of them use steam.) Having used both types, the end result appears to be the same, although if you have heavily trafficked areas or don't routinely remove shoes, it might be a good idea to get a home carpet cleaner that heats the water. Otherwise, you can simply use hot tap water or even heat water on the stove.
Know that all carpet cleaners require consumers to use their brand of detergent. Meaning that the best home carpet cleaners are the ones for which you can easily source detergent. Check your grocery store to see what carpet cleaning detergent brands they carry (it's usually Hoover) and try to buy a carpet cleaner to match the detergent. Otherwise, you'll forever end up having to make special out-of-the-way trips or place internet orders to obtain detergent. Having done this, I can attest that it really becomes annoying over the 3 to 5 year life span of a carpet cleaner. The last thing you want to do is spend years driving half way across town for carpet cleaner detergent. Been there, done that, not doing it again!
Check the warranty as one way to identify the best home carpet cleaners. Longer warranty periods often mean that companies expect their product to perform for at least that long. Short warranty periods tend to mean the product is made to have a shorter life span and will have to be replaced in just a year or two.
Read consumer reviews on websites. Consumer advocates such as Consumer Reports have not conducted extensive product testing on steam cleaners, so there are no official buyer recommendations. It's all anecdotal consumer experience. Fortunately, there are only four manufacturers to choose from; Hoover, Bissell, Kenmore, and Dirt Devil. Spend some time learning what actual consumer experience has been with each of these manufacturers.
Try not to spend more than $200 on the steam cleaner. It's really not necessary and price is rarely tied to quality when it comes to home carpet cleaners or vacuum cleaners. Focus less on price and more on making sure detergent is readily available as well as isolating the features that make the best home carpet cleaner for you.