I've recently started to try my hand at making puff pastry dough and in my first attempt I learned several very valuable lessons. At first, I added far too little water into the dough (about 2 tablespoons cold water in a mix of about 2.25 cups of flour and 1.5 cups butter) and got a crumbly dough that turned into brittle disks that disintegrated in my mouth after biting into it (quite an interesting sensation, actually). So, with the remainder of the dough I added another half cup of water, reworked the dough into a workable consistency and performed the folding procedure. In the end I got a dough that was very flaky, but brittle (not to mention the fact that I overcooked it a bit). My final sin on the first try was that I had to work the dough a lot to incorporate the added moisture, so that would've helped toughen it up as well.
I was wondering, what are your recipe for getting a flaky, but not overly tough puff pastry dough? A bit less water? More/less butter? Substituting butter for lard or shortening?