Do what I did and Brett is doing. You need to basically scalp the lawn. Make sure to kill off any weeds. Once that is done, you need to dethatch/aerate the **** out of it to give the seed good soil contact. Find a good seed and starter fertilizer and rake into loosened soil to cover seeds just enough. Keep the ground you overseed moist but not drenched. I was watering a couple times a day to keep mine moist.