I don't actually know what I do right, but this recipe always works for me. It makes soft, largeish cookies - the kind you get fresh in packets from Sainsburys (or probably other supermarkets). Quite sweet but yum.
Hi. I second chilling the dough for 30 minutes. If they are drop cookies, try leaving them in a ball rather than flattening them. Don't go overboard on the baking soda and powder - it can give them a chalky flavour. Good luck!