It is very important when making pastry to keep all the ingredients as cool as possible.
Do not overwork or over-roll the dough.
Handle lightly and as little as possible.
Knead lightly, roll lightly. Never stretch pastry.
To prevent a soggy base, using a pyrex pie dish is preferable. The heat tends to circulate better. If you only have a ceramic pie dish, then add 15 minutes to the baking time. Cover with aluminum foil for these last 15 minutes so that the top of the pastry doesn't burn but so that the bottom can continue to cook through.