Question: Do I need to add compost to the soil as I work it?

Answer: No. Your grass is going to have to grow in the native soil that you have. Rototilling alone should be sufficient. If your soil is too shallow and rocky, consider bringing in additional sandy loam topsoil. Be certain, however, that it contains no weeds that will be difficult to control (particularly nutsedge or dallisgrass), and be sure you’re not changing the water flow patterns in a way that might divert water into your home.