We had all weeds in our backyard when we bought the place June of 08'. We didnt start working on the lawn back there until spring 09'. My husband mowed it all down (as if it was grass), we watered, overseeded, fertilized and used weed killer for the summer of 09' and 10' This year we have a gorgeous lawn.

If I were you I would airrate, overseed, use a starter fertilizer and water. Overseed again in the fall. Keep up on fertilizer, weed killer and water. Overseeding in the spring and fall you should have a nice lawn in no time at all.

I wouldn't use a starter fertilizer because the soil around here generally has plenty of P and K. I wouldn't fertilize at all until the fall, unless you're using something really slow release like an organic fertilizer. If you have a starbucks handy, stop in and get their grounds for the garden and spread them around the lawn (no more than 1/4-1/2 inch deep). That will add a small amount of nitrogen and also encourage worms and increase the organic content of the soil.

I'd seed ASAP, but you may need to seed again in the fall since it's likely to be getting hot by the time your seed gets started this spring/summer.