Chat up your hairdresser and figure out what your hair type is. Hair type refers to the diameter of your hair strands, such as fine or thick. It also refers to the texture of your tresses, such as coarse or smooth. Nix any style of roller that isn't suited to your hair type. The general rule is that fine and thin hair is more delicate and thus needs a softer roller, such as foam, while thick and coarse hair needs a slightly harder roller that has a tighter clip or cap for holding strands where they belong.
Look at the overall design of the rollers and read product reviews to get a sense of how damaging each type of roller could be to your locks. Keep "little to no damage" as your guide. The rollers that tend to be gentlest on hair are flexi-rollers, satin rollers and foam or sponge rollers. Brush rollers tend to be the harshest and thus generally aren't used by stylists, but they might work for you if you have truly unruly hair that won't stay put in other rollers.
Determine what curl style you are after. Not all rollers produce the same type of curl. Some, for instance, are designed to wrap the hair vertically in preset ridges, while others are made to roll horizontally. Some are even in funky geometric shapes like triangles so they make a kinkier pattern. The diameter of the roller determines how loose or tight the curls end up, too, with larger rollers generally making looser curls.
Read the instructions to ascertain whether you can rock the curlers wet or dry. Ideally, you want rollers you can use either way, but some are much better suited to one moisture level or the other. For instance, mesh rollers are mostly open, which means your mane dries in a flash. Satin and foam rollers will absorb some of the moisture from wet hair, but because there's no heat to evaporate it or holes to let it out, hair can take a long time to dry and is better left overnight or blown dry. Check the heat settings if you're looking at hot rollers. Stay away from ones that get overly hot -- meaning you can't handle the roller right out of the heating tray -- as too much heat can rob your hair of moisture.
Feel the roller in your hand, getting a sense of its weight. Look for anything that could poke you or make your hair get caught. Comfortable rollers are a must-have, especially if you plan to sleep in them.
Look at the material from which the rollers are made. The last thing a fashionista needs is rollers that break easily, but you also don't want material that is ultra-expensive and therefore harder to replace. Hard plastics tend to be a good bet, but they might not suit the look you're going for.
Scope out the length of hair you have. Stick to smaller rollers if you've got short hair. A good rule of thumb is that the roller needs to be small enough for the hair to wrap around it at least twice. Bigger rollers are better for ladies with longer manes.
Take a gander at the price tag, as well as any "extras" that come with the rollers such as a warranty. As a general rule, if the rollers cost more than you'd earn in a day, pass unless you know that you'll use them without fail every day and the rollers get awesome reviews. The cheaper your rollers are, the less likely they are to have a warranty.
Even though you should read the manufacturer's instructions for use on any roller, take manufacturer assertions about what rollers are best with a grain of salt -- they want all their products to sell and often try to persuade people that rollers are more versatile than they really are. The same is true of hair care representatives or salon workers paid on commission.
Trying a roller out on your hair can be a good way to make a final pick from your final roller candidates, but don't roll all your hair in the rollers the first time out. If you do, any damage or poor results will involve your entire mane, not just a small section. Do a test roller instead.