Tiga
Here are the two starters I use most frequently in this book and in my restaurants. Tiga is my slightly more hydrated version of a classic biga starter, which is usually between 50 and 60 percent water. This "Tony's biga," which I call "Tiga," has 70 percent hydration.
My poolish follows the traditional proportions of equal parts water and flour, so its hydration is much higher at 100 percent. In general, unless I specify otherwise, use the same flour in your starter that you will be using in your dough. I always make starters with cold water to slow down the fermentation process for greater flavor complexity. It's helpful to use a clear glass bowl so you can see how well your starter is fermenting.