Whether you want to admit it or not, braking is the hardest part of longboarding. And one of the most difficult to master. Beginners are usually afraid of starting to longboard or skateboard because slowing down is so intimidating. Here we will go through a few methods to control and lose speed effectively, ranging from easiest to hardest.
The most basic method, usually used to get the feel of your setup or gain steeze points, most people learn this to keep their speed low while going down small hills. Increasing the amount of distance you're covering and making large, smooth, continuous turns will keep your speed on the more manageable side until you get down to the bottom. This will not fully stop you.
One of the first ways people learn to control their speed, this is preformed by taking your pushing foot off the board and placing it LIGHTLY on the ground next to your balancing foot. By increasing the pressure on the ground, you can control how much speed you lose. This does wear the sole of one shoe down significantly, especially if you find yourself doing this a lot. A Roger Bros Brake Sole will save your shoes a bit longer, and are fairly easy to find and/or make.
Usually done at high speeds to when riding close to another rider, standing upright with your arms outstretched to create the most amount of air resistance will slow you down a bit. This is handy when entering turns to slow down a bit and make it more manageable, as well as adjusting your position if you're pack riding. This will not fully stop you.
Definitely the most effective of these methods, when done right sliding can bring you to a stop quicker than a bike. It takes a lot of practice to master this technique, but if you ask anyone who can slide, it opens up everything for safe riding.
If you're doing a lot of foot braking and wearing down one shoe too much, you can sit down on your board and use your other foot to stop, evening out the wear. What you have to do is balance on your front foot and slowly lower your body as much as possible. When you're ready (you'll know when) you put your butt as far forward as you can and put your feet in front of you. Some people do this in one motion, others do a little jump to put their rear end where their foot just was. It depends on how comfortable you are with riding.
As a last ditch effort to stop yourself, you can run off your board if you're going slow enough. Only do this if your running speed is faster than how fast you're skating. That way your feet wont get caught up under you and you'll be able to run out safely.