Wnat to stay and travel america for 6 months?

im from the uk and know that i can stay in america for up to 90 days as part of the visa waiver program. but i would like to stay for 6 months. how do i go about this? do i make an appointment at the american emby in london to apply? how long will it take? what should i expect? im planning on staying with friends and i dont intend to work as i have saved enough money already.