Pressure Plates. How do you make them? Go to your crafting box, take some stone, put two next to each other and note this needs to be stone, not cobblestone. As you can see, it won't work for pressure plates and buttons, that is. Now, to use your pressure plate, you can simply just put it down in front of something and step on it. If it is touching the adjacent block, then it'll set off whatever object it's next to. Now, another way would be if you want to have the switch somewhere else, you can just run a line of redstone, and there you go. Easy peasy pressure plates.