Once you've got all the pedals that you want on your pedalboard it's time to measure their dimensions. Because when you know how big each pedal is you also know how big your pedalboard needs to become. So get that ruler in your hand and write down on a piece of paper how big every pedal is, height and length. When this is done the planning part begins.
Think of the order of the pedals and try to put them as close to each other as possible to avoid long cables running back and forth across the board. And don't forget about the power supply inputs, those little plugs also takes up space and can sometimes get in the way of your plans. Draw your layout on a paper (I like to use lined paper, the once you use on the math class in school, and think of one square as 1x1 cm) and do it with great accuracy so you won't get any nasty surprises later on. I like a setup where small pedals is fitted in two rows and bigger pedals, like a wah-wah, takes up two rows by itself. I also like the idea of an angled pedalboard for several reasons - its easier to reach the pedals on the upper row and if it's angled enough you can put the power supply under the board, which saves space for other units. Sometimes it can also be beneficial to put one pedal vertical instead of the classic horizontal look, it can really save you some space. Play a little game of Tetris with your pedals and you will hopefully find your ultimate layout. Just make sure that the switches on every pedal is easy to hit, so it won't get hard to turn on and off effects.
Then there's the material issue. You would want a pedal board that can take a hit without breaking but on the other hand it's nice if it isn't too heavy. It's good if your board is easy to transport, but it's also good if it can last for some gigs (or preferrably, world tours). I've seen both wooden pedal boards and those made of steel. Make sure that you settle on a material that's well suited for you because once you do, there's no way back.
Another feature that is great when you want a tidy, functional pedalboard is to leave some space for cords and cables to go under the board. This way you won't have a spiderweb of cables on the board, which could get in the way of the switches or unplug some pedal in the middle of a song. When I designed my pedalboard I built it around several bars with a few centimeters distance. This way I could fit all pedals on the bars, hook them up with velcro tape and have much space under the board where I could drag the cables and place the power supply.
There are of course a lot of pedalboards on the market, some with their own power supply (I would avoid these, it's always better to use exactly the power supply that you want), some angled, some with a softcase and some with a flightcase. These boards comes with certain measurements and if some of these would fit yor pedals - great. Chances are, however, that they won't be the best solution for your effect pedals. If you don't want or can build a board yourself, look up a maker of pedalboards. This is often an expensive deal but you can get your board customized just (well, at least almost) as you want it. But if you've got the oppurtunity to build yourself, or with the assistance of a friend, draw a design and get started. Your own imagination is the only limit. You can make a curved board, you can make a board with an extra level for one pedal that maybe needs a bit more space or you can make several boards and tie them together. Take it step by step: measure, plan and design. And start all over again if you're not satisfied with what you come up with.
Here are the design that I wrote for my three pedalboards, and under them are some inspiration for you: