Installing sod instead of planting grass seed allows you to have a green lush lawn right away. Keeping the sod green and healthy will depend on how it's installed and cared for while the roots are establishing and growing into the soil beneath the sod. There is a right way and a wrong way to install and care for new sod.
Don't lay sod on soil that hasn't been prepared. Prepare the soil by removing debris and weeds. Sod cannot be laid down over grass and weeds. Use a rototiller to break up the soil so it's not compacted. Loose soil will allow the sod's roots to grow downwards into the soil to establish a healthy root system. Compacted soil can prevent the roots from penetrating the soil for good root establishment. Level the ground with a hard rake so the sod doesn't stick up in some places and dip in others.
Sod seams are butted together so that you cannot tell where the seams are and, as the sod shrinks a little after installation, you won't have empty space between the sod pieces. When sod is laid, the piece is placed so close to the next piece of sod that it almost looks like it is overlapping slightly. Pound the sod down with your foot or hand so it is level with the piece of sod already installed to ensure the seam is invisible and tight. Stagger the seams in each row; don't line up each piece of sod so the seams are all in one place on each section.
After installing the sod, get rid of air pockets between the sod and the soil. If you don't use a tamper or drum roller, the roots of the sod are not going to grow into the soil below. Tamp down every inch of the sod. With a drum roller filled with water, you can walk back and forth on the sod to flatten it down and remove the air pockets.
As soon as you install sod, you must water it to keep it moist. Don't wait until the next day, or the sod will start to die off. Sod requires a strict watering schedule for the first and second week until the roots are established in the soil underneath. During this time, only walk on the sod to set out the sprinkler.