1. Rehydrate dry yeast. Some folks worry about osmotic shock and then make a practice of rehydrating dry yeast in warm water before pitching into wort. Please don't rehydrate in water. Rehydrating dry yeast in water can strip your yeast of essential free amino nitrogen (FAN) that is needed for growth and proliferation. Rehydrate in wort (just sprinkle over the top, don't stir, don't do anything but sprinkle).
2. Vorlauf or Wort Recycling in the mash The collecting of wort as it runs out of the lauter tun and pouring it back over the grain bed is commonly practiced. Many brewers claim that recycling should be done to settle the grain bed. Please don't recycle. This practice can not only lead to hot side aeration, but will strip out fatty acids that are essential for proper yeast nutrition. In particular, North American grains tend to be low in fatty acids to begin with, so please don't Vorlauf domestic grains.