Usually I just shuffle the cards until the deck feels "ready." Sometimes it takes a long shuffle, sometimes the deck feels ready almost instantly. Like HearthCricket, I never second guess it either, I've learned to trust my intuition. I've noticed that if I second guess, and happen to use the Thoth, the deck throws a temper tantrum and refuses to cooperate.
Then I usually just deal from the top, but sometimes I feel like dealing from the bottom, and when that happens, I'll follow my instinct. So, I may end up dealing some cards from the top, some from the bottom.
Sometimes, if it's a big spread, I shuffle the deck and cut it into three piles. I select one of the piles with my left hand, eyes closed, feeling the energies of the piles, pick the one with the strongest energy (warm, tingling sensations), and deal from the top of that pile.