The definition of pastry is a dough that is made of flour, water and a fat or oil, which is then baked. It isn't complicated. Nevertheless, many have a fear of making pastry. Here are a few tips for better, flakier pastry.
Most pastry, whether it is pie dough to biscuits, need to be handled as little as possible. Many novice cooks will want to overmix the dough. Overmixing dough will make dough tough. The lightness and flakiness happens specifically because fats and water don't mix easily. So, it is important to leave the dough not well mixed so it can produce those layers.
I have been experimenting with pastry from whole wheat flour. White flour certainly produces a much higher quality flake, while whole wheat flour tends to produce a more crumbly, tender pastry. For those of us trying to incorporate more healthful foods (including whole grains), but love pastries, the difference in texture may be worthwhile. But, it is important to still not overmix so that the dough stays tender and not tough.
The exception to the rule about not overmixing is when yeast is added to the mix. Yeast doughs become more tender the more they are kneaded. For this reason, unless you experience the zen of kneading by hand, the most convenient and most consistent way of kneading the dough is by using a stand mixer with a dough hook.
As other ingredients are added, the dough is altered for other types of pastries. When egg is added, it becomes dough for danish. If the egg is cooked into the dough as it is added, then it is dough for puffs, as in cream puffs and eclairs.
Your choice of fat used will also have an impact on the texture. The most flaky pie crust comes from using lard. But lard is not something most of us want to ingest any more and so we step down from that pinnacle of high cholesterol, non-redeeming fat to shortening for the next best texture. Using butter will produce a more crispy layer, while using vegetable oil will produce a more tender layer.