Summarize:

Pedal boards can be bought off the shelf or customized to your particular set-up. Whether you choose a small, medium, or large pedal board generally depends on the number of pedals you're using on a regular basis and the size of those pedals.  Generally, if you're using five or fewer pedals, you want a small pedal board. For more than ten pedals, on the other hand, you want a large pedal board. Also take into consideration if you plan to add more pedals over time. For example, if you currently use four pedals but plan on adding three more, it's best to go ahead and get a medium-sized pedal board so you'll have room for the others when you get them. If your pedals are oversized, you may want to get a large pedal board even if you're only using four or five pedals. This will prevent overcrowding. Whether you're buying a pre-built board or building your own, you need to make sure the pedal board will power all your pedals. While most pedals require 9 volts of power, some require more.  Be sure to check the power requirements of every pedal in your set-up – don't just assume they're all the same. You also want to check the power requirements of pedals you plan to add later on to ensure the board you buy can handle them. Your power supply needs to have the correct voltage as well as be able to handle the number of pedals you have or ultimately will have once your set-up is complete.  For example, if you have 10 pedals, all of which require 9 volts, you'll need a 9-volt power supply capable of handling 10 or more pedals. If you have one pedal that requires 12 volts, you'll need to look for a power supply that allows you to isolate pedals, because you don't want 12 volts running through the other pedals that require less power. While you do want to leave a little bit of space between pedals on your pedal board to keep it from looking cluttered, you still want to use extremely short patch cables to preserve the quality of your sound.  Choose cables with right-angle plugs rather than straight plugs, and this will cut down on the amount of space the cables take. If you have the tools to do so, you can pretty easily cut your own cables, which can both save you money and ensure that your cables are the exact length you need for your particular set-up. Avoid black cables, as they can get lost on a stage and you may not be able to easily identify the problem if one is unhooked or damaged. Because you may want to change the order of your pedals to alter your guitar's tone, use a non-permanent means such as Velcro to fix the pedals in place on your pedal board.  Particularly if you're working with a large number of pedals, you may want to stagger them so they alternate between the front and rear edges of the pedal board. This will make it easier for you to differentiate between them and hit the pedal you want during a performance. Make sure the pedals you use most often are laid out so they are easiest for you to reach with your foot. Keep in mind that the location of the pedals on the board doesn't necessarily need to follow the signal chain you've created exactly. However, you do want to follow it as closely as possible to reduce the length of the patch cables.
Choose the right size. Check the power requirements of your pedals. Find an adequate power supply. Use compact patch cables. Velcro your pedals to the board.