My lawn is giving me difficulties it grows strangely and grow with alot of unwanted weeds?

i need some really good fertilizer to make it greener and kill all those unwanted weeds. Before that i want to aerate the ground and use a thatcher to get rid of all the dead stuff. What are some good tips on which exact fertilizers to use to kill all those unwanted weeds and make the grass greener. By the way I live in New York and its summer time already.