Answer: Sod (of cool-season grasses) can theoretically be laid any time during the growing season, but it has far and away the best chance of becoming established and thriving if planted in the early spring or in the early fall. The reason for this is that the weather and natural rainfall are most favorable then. The soil preparation is extremely important and should be done on the basis of soil tests. You can run these tests at any time the ground is not frozen. The actual loosening of the soil and adding of needed amendments (as indicated by the tests) is usually done shortly before the sod is brought in. If done too far in advance, the soil may erode badly or it may become compacted before the sod arrives.
Since this is an expensive and fairly complex process, I would suggest you work with your county extension on interpreting the soil tests and determining how best to prepare your soil for the sod. You might also want to read up on it a bit. A book I particularly like on lawn care is "Lawn Care for Dummies" by Lance Walheim, ISBN 0-7645-5077-2. In it you will find straight forward discussions of soil preparation, how to select the most appropriate grass types for your yard, and how to install and care for sod -- as well as starting a lawn by seeding. Good luck with your lawn!
Q&A Library Searching Tips