The first consideration in choosing a perfect railing is safety. Before purchasing any model, read if the manufacturer follows any safety standards. These can vary from state to state, but the basic rules are:
Baluster spacing or the opening between balusters shouldn't exceed four inches.
Railing height requirements vary significantly. The most commonly used minimum height is from 36 to 42 inches from the surface to the railing top. You can find information about it on a package or ask a salesperson for additional information.
Style, architecture and other design elements
It's highly recommended to match your railing to the design of your home because it is going to be seen from anywhere in your house, be it near or far, for better or for worse. Thus, railing is one of the most important decorative elements. The color, style and size of the railing usually have a huge impact on the feel and look of your interior, and can help blend several floorings together. As a rule of thumb, the railing should complement the other details of your house by having matching colors and being in the right proportion with them.
Possible exposure to sun, water and other elements
Environmental factors play a huge role in the appearance and function of your railings. Choosing a dark metal rail isn't the best decision for a deck that will be exposed to UV lights in a tropical climate. A glass railing within reach of dirt or dust will look just awful, and glass balusters can increase the temperature on the surface in hot climates while cutting down on airflow.
Choose the right color
Not all rail types are available in many colors, so keep in mind that it can be a tricky task to find a perfect model. For example, if you want a white railing it's better to first search for models that come in white and then look at their type. Some manufacturers have a limited color range, especially for expensive railings. However, cheaper options often have a nice variety of colors that allow you to match or contract with details of your home. Note that the darker the color of your railing, the clearer view through it will be achieved.
Before purchasing a railing, think how much time you can spend maintaining its look. Traditional wood railings are labor and time intensive to maintain, so choosing a different material (a metal railing, for example) can free up a lot of time. Glass balusters or panels may also require additional treatment to minimize spotting, but copper and several types of aluminum are maintenance free.