Your seat must fit your type of riding and your body. The faster you ride, the more likely it is you’ll want a narrow, racing-style seat. This is because, a fast-riding position on a bike shifts you forward placing more weight on the hands and feet and reducing a lot of the weight on the seat. Also, as you pedal more vigorously, you spin faster and you can’t tolerate interference from the sides of the seat.
As you ride more casually, however, such as on a cruiser bike with wide backswept handlebars, most of your weight is planted directly on the seat. Plus you don’t pedal quickly at all. These factors make a wide, heavily padded saddle ideal to support your weight and provide cushioning.
Equally important, most manufacturers offer their popular seat models in both men’s and women’s versions and there are significant differences.
Because male and female pelvises differ (women’s are wider), it’s usually (though not always: women sometimes do fine on men’s seats) a good idea for men to start with men’s saddle models and women with women’s. The former is a bit longer and narrower while the latter is a bit shorter and wider.
Next, the seat must fit your particular anatomy. You can sometimes see how you fit a seat if you sit on it for a while then get off and immediately look closely at the back of the seat top. If a saddle is right for your body, its rear will support your sit bones (the ischial tuberosities - those two protrusions that bug you when you sit on a hard bench). These bones will form dents in certain types of seats. If the seat is correct for your anatomy, the depressions will be centered on the pads of the seat on either side.
While the rear of the seat supports your sit bones, the front (nose) of the seat is designed to help you control the bike with your thighs and support some of the body weight.
The problem with the nose of the bicycle seat is that it bothers many riders, both women and men. This is the part of the seat that’s most likely to compress nerves, irritate genitalia, cause chafing and generally abuse the body. Fortunately, there are plenty of seat models currently available that address the issue with various innovations.
Certain models incorporate a channel centered down the length of the seat. Others use a hole toward the front of the nose. Seats with channels and holes are often called Cutaway seats. Some seats feature soft foam or gel in the nose and soften the base of the seat beneath to reduce the stiffness. These are usually called Gel seats. The important thing to know is that if you find the seat’s nose a problem, there are models designed to remove the intrusion. Try a few until you find the model that works for you.