Most of this is quoted from a previous post.
The more common way of being taught how to perform the shuffle (e.g. in Card College - where I initially learnt it) is to weave the cards short end to short end, but it is also taught corner to corner. What I have found is a happy median is best - square the two halves and place them end to end, which helps to keep the cards square, and then, concentrate the pressure of the weave upon the corners nearest you - this helps keep the weave tight and also works if card edges become a little frayed as well, as corners tend not to become as easily frayed.
Secondly a firm but gentle grip is required. This is probably the best piece of advice (one that Giobbi gives along with many others). The grip I use changed over the period of learning the shuffle, in that my two thumbs have come a lot closer together during the weave. This keeps it much tighter and under much greater control. I can't emphasise enough how helpful this is. If part way through the weave you see it about to go wrong it is possible with a kind of 'pulling' motion of the fingers to correct for it. Unfortunately, this is just a knack.
As for cutting the deck in half, this is a challenge in itself, but what will help is making sure the deck is tightly gripped when cutting. If they are loose, then the cards will spread out slightly, and what will look to be two sections of equal width won't necessarily be two halves of the same number of cards. If you want to demonstrate taking a deck from new order, and back again, you can simply remember what cards to cut to.
Hope this helps. I also recently posted a performance of the faro shuffle.....
Here