Who ever made up the phrase "easy as pie," was a big fat liar.

Dear Tricia,
What's the secret to good pie crust? I've tried to make it from scratch before but it wasn't flaky like I wanted. What did I do wrong?

Oh, pie dough. It seems so simple and unassuming, doesn't it? 4 basic ingredients, a basically simple method... but it goes wrong so fast, just like Lindsay Lohan's career.
The trick with pie dough is that you have to use really cold ingredients. Let's go over the basics, and then I'll bust out some fancy science. Take a look at your average pie dough recipe:

1 1/2 cups plus 2 tablespoons flour
1/2 teaspoon salt
1 stick cold unsalted butter, cut into 1/4-inch pieces
2 tablespoons solid vegetable shortening
3 tablespoons water

1. Mix flour and salt together.
2. Blend cold butter and shortening into flour until the butter resembles the size of peas.
3. Add water and knead until it becomes a dough.

Easy as pie, right? No. It's all wrong. These directions are going to give you really crappy pie dough. I think they're doing this on purpose so that you'll keep going back to the store and buying more cookbooks. I don't know who "they" are, but I'm sure they're mean and have beady little eyes. But back to the pie dough.
First of all, you don't want 1/4" pieces, you want more like 1/2" pieces. To get really flaky pie dough, you need large pieces of butter and shortening. Small pea-like pieces will give you more of a shortbread-like dough. And you didn't ask for that, did you? (Wait... let me check... nope, you asked for flaky dough. Just making sure I wasn't wrong.) With your hands, and not a mixer of any kind, just mix the shortening and butter into the flour and break it up so that the pieces are all covered with flour, and are BIGGER than peas. Work as fast as you can because you want the butter to stay cold and hard. If it gets too soft, just put the whole mix into the refrigerator for 10 minutes or so.
The water that you've measured out needs to be ice cold. Just take a glass of ice water and use the tablespoon to measure out the water from that. The colder the better because you don't want to soften the butter. When you're done mixing the butter into the flour, take your ice cold water and start mixing it into the bowl. Use your hands and gently form a dough, no kneading-necessary. The more you mess with it, the tougher your pie dough will be.
Once the dough is formed, let it chill for an hour, then roll it out, put it in the pan, and then let it chill again before you bake it. You can even freeze it before you bake it. The point is to keep the butter cold cold cold. Have I mentioned that yet? Once you bake the dough using this method, I guarantee you that it will be flaky as Janet Jackson was on her latest concert tour.
Want to know why you have to keep the butter so damn cold? Well, I'm so glad you asked! Butter is partially made up of water. When its super cold and then goes into a super hot oven, the water quickly evaporates and makes steam. The steam is what puffs up the dough and makes it light and flaky. If you were to take a room-temperature pie dough and put it in the same oven, the butter would just start to melt everywhere because its already so soft, giving you a soggy pie dough. Get it now? Super cold butter= super flaky pie dough.
And I have to address the shortening and butter combination because a lot of people ask me "Why not just use all shortening or all butter?" Because butter is so temperamental and you have to work hard to keep it cold, adding a little bit of shortening gives you a little more leeway to get a better dough. Shortening also makes it easier to roll out. And the reason why you wouldn't want to use all shortening is because that's just gross. Shortening isn't a real food that your body recognizes, it doesn't have the flavor of butter, and it leaves that weird coating in your mouth that sticks around for like 5 hours. Using it in moderation is fine (just like anything in your diet,) but stick with a mostly-butter pie dough for good flavor.