For an average sized lawn the first thing to do is to till it up after it has been leveled and add any soil amendments needed. Rake it smooth. Decide what kind of seed you need; sunny shady or a mix. If you have good sun I would go for a water miser seed. When you plant the seed the soil needs to be 56 degrees or warmer to germinate. Test for PH ( You can get a small kit at the store) and add lime as needed; you will probably need lime so if you do not test add some any ways. New lawns need fertilizer to help them grow, use one without any added poisons like weed killer. You can even get an organic based one. Use a spreader to spread lime first then fertilizer and then seed. You can get a push spreader for a good price. Lightly rake it in and use a roller to push it in and smooth the lawn. Keep the seed and lawn watered.
Do not mow until it is well established.