Bicycle Fit:
Proper bike fit is important. A bike that's too large or too small is difficult to control and can lead to discomfort or injury. As a general rule for road bicycles, you should have at least one inch of clearance between the top tube and your crotch as you stand astride the bike. Clearance should be approximately two inches for a hybrid or cross bike and three to four inches for a mountain bike. Ask your bike shop for help fitting your bike.

Outfitting Your Bicycle
You don't have to spend a lot of money on gear, but certain accessories can make bike commuting safer and more enjoyable. Prioritize spending on safety-related items. Keep in mind that you get what you pay for, and since bike commuting is very economical, you will save money in the long run. To make choosing among the wide variety of bicycle accessories a less daunting task, think about your needs, talk to friends and staff at your local bike shop and read equipment reviews in bicycle publications.

Headlights & Tail Lights
Headlights are required by law for night riding. Taillights are a good addition to the rear red reflector. Lights vary greatly in their quality of construction, mounting design, amount of light supplied and duration. Headlights are divided into three categories: rechargeable, non-rechargeable, and generator. Each has advantages and disadvantages. Battery-powered LED (light-emitting diode) lights are long-lasting, light weight and reliable.

Tools
It's a good idea to carry a basic tool kit with a small set of allen wrenches, a tire patch kit, and tire levers. Flat tire repair is often featured in bicycling magazines and is always included in repair manuals. Products such as puncture-resistant tires, tubes and tire liners can help prevent flats. Inquire at your local bike shop. Including a rag in your tool kit can help you stay clean in the event of a mechanical problem.

Fenders
Fenders help in wet conditions. They nearly eliminate spray from your wheels, keeping you drier, cleaner, and more comfortable.

Mirrors
Some cyclists use mirrors to keep track of traffic behind them. Mirrors come in two basic types: head-mounted and bar-mounted. Mirrors mounted on your helmet (or eyeglasses) are constantly in your field of view, requiring just a quick glance to check the road behind, but some find them distracting. Bar-mounted mirrors are not in the field of view, but often are subject to vibration from the road. Although mirrors can help you keep tabs on traffic, they are not a substitute for looking behind you before changing lanes.

Hauling Items
There are practical ways to haul items such as laptops, work files, extra clothes etc. for daily commuting; or items carted for personal trips to the store for groceries and other purchases. Various methods include the use of messenger bags, backpacks, baskets and panniers. Each has its own advantage, depending on your need.  Panniers are loaded in such a manner as to distribute weight evenly on either side and there are many styles available.