When pushing your pastry into the sides of your tin or pie dish, ensure that the pasty along the sides is a little thicker than that of the base. To do this push the excess that overhangs the sides down into the tin, to create a thicker layer. Run your rolling pin over the top to trim off the excess pastry in order to give a neat finish and then squeeze the pastry on the sides up a little so that it is slightly raised above the edges by about half a centimetre. This will ensure your pastry keeps its shape whilst allowing for shrinkage in the oven as it bakes.