You will always have weed seeds in the ground. Keep them under control by growing lots of good quality grass which keeps the weed seeds shaded so they won't germinate.
If you want to do a real good job then take soil samples and have a test done. That way you will know whether or not to use fertilizer and if so how much.
As for seed you will have to choose whether you want a warm season grass or a cool season one. Personally I use a cool season grass which comes on early in the spring, goes dormant in the hot summer and rejuvenates in the fall (tall fescue).