be patient. let mother nature take care of it. if you really want nice lush uniform lawn right away, you can have it. All you need to do is write a check.
In New England, the best time to plant new grass is early fall. Since most grasses can't handle the summer heat so well, spring is not the best time. But again, this year is weird. It already snowed twice here in October. Maybe we should hold off this fall.