Hydration is the percentage of water by weight to the weight of flour, e.g., 60% hydration for 1000 grams of flour would be 600 grams of water. Here's a good example of how it's used in the context of pizza: http://www.varasanos.com/PizzaRecipe.htm
Unfortunately, a kitchen scale is essential. But here's a no-knead recipe from the person who developed it: http://www.sullivanstreetbakery.com/recipes