What's your hair type? Different hair types require different levels of heat. Thick and coarse hair needs stronger heat, while fine or thin hair needs less heat. A lower-powered dryer is also a good choice for setting curls or blowing dry bangs, since you can take your time without frying your hair. A cool shot feature is also essential for curls, whether natural or created with rollers, as it cools down your hair and sets the waves in place.
What's your noise tolerance? It might seem like more powerful hair dryers would naturally make more noise, but in reality, high-powered salon dryers are generally a bit quieter than cheap hair dryers. Think about how much noise you can personally put up with, and also about who else might have to listen to your dryer—your partner, your roommates, total strangers at the gym?
How strong are your arms? It may sound silly, but the more upper-body strength you have, the less crucial it is for your hair dryer to be lightweight dryer. On the other hand, if you have especially long or thick hair, weight becomes more important, because you'll be using the dryer for longer at a stretch.
Will you travel with your dryer? If you travel frequently, a compact and lightweight dryer—particularly one with a folding handle—takes up less of your precious suitcase space and weight. However, travel dryers don't fare as well in reviews as full-sized ones, so don't buy a travel dryer if you'll mostly be using it at home. If you often travel outside the US, a dual-voltage hair-dryer is a must for running on European current—but they don't always come with the right plug adapters for use in foreign parts, so remember to pack a separate adapter if necessary.
Which attachments do you need? A diffuser, which distributes heat across a wider area, is a must-have for curly hair to prevent frizz and tangling. In fact, two stylists interviewed by the Huffington Post say that even for softer waves, a diffuser is helpful for adding body and bounce. A concentrator nozzle, by contrast, focuses the airflow in one spot and is most useful for straight hairstyles. Concentrator attachments generally come with the hair dryer, but diffusers can be purchased separately if your dryer doesn't have one; all you need to know is its diameter.
Read the safety instructions. In doing the research, we found numerous complaints about hair dryer failures, and even issues such as spontaneous fires. While many are, indeed, the fault of the appliance, many others look to be the result of misuse by the user -- for example, reports of hair dryers catching fire while not in use, but plugged in, despite standard warnings that hair dryers need to be unplugged immediately after use. The bottom line is that it is very important to read and follow all safety instructions when it comes to using a hair dryer. The Consumer Product Safety Commission (CPSC) offers additional information and safety guidelines.
If you're investing a lot of money in a good hair dryer that you expect to use for many years, it's reasonable to expect it to come with a decent warranty. However, the words "4-year limited warranty" on a product description aren't really enough to tell you how useful the warranty truly is. We found many reports of unexpected "gotchas" in hair dryer warranties that made them all but useless.
For example, multiple users who had problems with one Conair hair dryer say its warranty doesn't cover shipping fees, and shipping the dryer to Conair and back would cost more than replacing it outright. Bottom line: before you spend money on a hair dryer, read the terms of the warranty in full so you know exactly what you're getting into. This will also warn you about less-than-obvious ways to void your warranty, such as buying from an unauthorized dealer, failing to unplug the dryer or wrapping the cord around the dryer when storing it.