It is thought that seeds which follow this cycle and are outside to endure the cool evenings and warm days during the early spring form stronger plants than those that are coddled inside under lights and warm temperatures. This makes a lot of sense to me. In fact, there is a website devoted to the concept which gives suggestions and ideas about how to do this.
Then make drainage holes in the bottom. There are several ways to make the holes. One is to heat a nail over the stove and melt a hole in the plastic. However, I used a Dremel tool fitted with a small drill bit.