Your first decision comes in determining what type of bike you are after. There are basically four main styles of bikes to choose from, and your selection should really depend on what you anticipate your main type of riding to be.
Road Bikes are designed for riding on paved streets and going fast. Featuring skinny tires, a lightweight frame and a riding position that puts you bent over the handlebars, you might choose this type of bike if traveling longer distances at higher speeds is important to you.
The frames of most road bikes are not particularly beefy in construction and generally won’t stand up well for extended periods under heavy loads or on really rough surfaces.
They are about as well-suited for a path in the woods as wearing high heels to go for a jog on a rugged path.
Mountain Bikes have exploded in popularity over the past twenty years. These bikes have wide tires, usually with knobby treads and a stout frame, and are designed to handle the rugged trails without disintegrating. Mountain bikes do not go as fast as road bikes, which is a trade-off for their durability along with a more comfortable riding position. You sit higher on these bikes, more upright with the straight handlebars, which is often a happier choice for people with back problems than being hunched over as you are on a road bike.
Warning: sometimes mountain bikes are the default choice of salespeople at the bike shop because they are easy to sell and usually less expensive than road bikes. Too many times though, new mountain bikes with lots of impressive features for climbing a steep mountain trail end up like those four-wheel drive SUVs that never actually go off the pavement.
If you are going to buy a mountain bike, make sure you are doing so intentionally because you know that you will, in fact, be riding off-road. Otherwise, you will be paying for unnecessary features, and probably missing out on a bike that would be a better choice for you
Hybrid bikes are a compromise between road and mountain bikes and offer the best features of both if most of your riding will be shorter trips on the pavement. With skinnier, smooth tires, they typically can go faster than mountain bikes, yet feature the upright seat and handlebar position that many people favor.
Hybrids are a good choice for most city riding and offer speed, durability, and comfort.
Touring Cruiser Bikes
Cruisers are bikes that have wide tires, wide seats, upright handlebars and sometimes even just a single gear. These are the bikes that you’ll often see at the beach. More simple mechanically, they are easy to maintain but work best with flat terrain and a rider whose main interest is more about being comfortable than with going fast.
A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons: the rider's weight is distributed comfortably over a larger area, supported by back and buttocks. On a traditional upright bicycle, the body weight rests entirely on a small portion of the sitting bones, the feet, and the hands.
The tandem bicycle or twin is a form of bicycle (occasionally a tricycle) designed to be ridden by more than one person. The term tandem refers to the seating arrangement (fore to aft, not side by side), not the number of riders. Patents related to tandem bicycles date from the late 1890s. Tandems can reach higher speeds than the same riders on single bicycles, and tandem bicycle racing exists.
In the West, adult-sized tricycles are used primarily for recreation, shopping, and exercise. Tricycles are favored by children and senior adults for their apparent stability versus a bicycle; however a conventional trike has poor dynamic lateral stability, and the rider must take care when cornering to avoid tipping the trike over. Unconventional designs such as recumbents have a lower center of gravity so require less care.
Spend Some Time at Your Local Bikes Shop
The people who run the LBS are your best resource on bike buying. These folks are knowledgeable and can offer tips, advice, and service that you can never get over the internet.
A reader wrote about her experience buying from her local shop:
What ended up being the deciding factor [in my choice] was going to the bike shop and talking to the salesman about what I was looking for. I went in thinking I wanted one bike, but after talking with him and describing what I'd be using it for, it turned out I was really after something else. It was a great experience and I ended up with the perfect bike for me.