Preheat the Water
Preheating your water is very important for dishes that are cooked for a short amount of time. The temperature of the water can fluctuate wildly during the first 30-60 minutes, especially with cheaper sous vide setups, and can adversely affect the outcome of your dish if it is only in the water that long. For sous vide dishes that are cooked for five hours or more it isn't as important but preheating never hurts.Heavy on the Water
This is an important tip, especially for items cooked over a short period of time. Even if you preheat the water, when you put the colder food into the water bath the temperature will drop and the heating element will go into overdrive to bring it back up to temperature. The more water you are cooking in the less the temperature will drop. It can also help to let your food sit out for 15-30 minutes to come up to a higher temperature so the change in the water won't be as severe.Turn Up the Heat
Most meat cooked sous vide should be done with very un-fatty cuts. However, if you find yourself with a more fatty cut you can turn the temperature up to about 150°F which will help break down the collagen without drying it out completely. The same cut of meat cooked at 130°F will actually be tougher because of the excess of collagen.All Meat is Different
More and more people are purchasing meat from places other than the supermarket for a variety of reasons from better flavor and texture to healthier meat and more humane treatment. I'll save any lectures for another time but one thing is apparent, meat raised in different ways behaves differently when cooked. We've found that grass-fed beef roasts only need to be cooked for about one half the time of a comparable supermarket roast before they become tender. So be aware that meat from different places cooks differently, there's nothing worse than turning an expensive cut of meat to mush.