My back yard receives full sun all day and is next to a large lake. After two seasons of seeding I am debating whether or not to lay sod. Obviously, if I laid sod, I would lay zoisa, due to the heat and full sun. I have a medium sized yard. Like any home owner, I conveniently put down Scotts seed, and ended up with the usual results; weeds and bare spots. I guess my question is how do I prepare the soil, with weeds and grass intact for laying sod? And, How would I prepare the same soil with weeds and some grass intact if I laid better seed? Would simply tilling the area be good enough? Would a good heat tolerant and full sun seed work> if so what kind? Same goes for sod as my other option. I am in St. Louis if it helps. Thanks in advance.