Blind baking is really just another way of saying "pre-baking." It simply means that you bake the pie crust on its own before adding the filling. This is something you do if the filling itself isn't going to be cooked (like a fruit tart) or if the filling will cook faster than the crust (like with a quiche). You can also either fully bake the crust or partially-bake it so that it has a head start when the full pie goes in the oven. The recipe should specify how far to cook the crust.
There are two ways to go about blind baking: docking and using pie weights. Docking involves pricking the crust with a fork to allow steam to escape evenly. Otherwise the crust will tend to bubble up and cook unevenly.
Pie weights do the essentially same thing by pressing down the crust and holding it in place. You can buy fancy ceramic pie weights or simply use a dried beans. Either way, put a layer of parchment between the crust and the pie weights to keep the pie from picking up any off flavors from the weights, and push the weights all the way to the edges to help keep the sides from collapsing during baking.
For either method, bake the pie crust in a 425° oven until the edges are brown and golden. Allow 30-40 minutes for full baking or 25-35 minutes for partial baking. If you're using pie weights, remove them halfway through cooking so the steam can escape and the bottom can fully cook.
Now, who's ready for summer pie?!