Basically this question is a tough one but indeed interesting to answer. I haven't been in a hookup relationship however if I will be and wanted to end it up, it is better to end it up nicely and gracefully by letting him know that "his" benefits have been revoked.

First and foremost, I will stop the "intimate stuff" we do, ignore any means of communication like chat, text, or call then I'll give time for myself to think how to say it honestly to him. Then when the time comes that I'm ready, instead of going to his place, I'll beep him and ask to meet in a restaurant or in any place where we can't be alone.

If my invitation will work and his already in front of me like having dinner together, I'll start it by telling him how wonderful having an intimate relationship with someone we truly love and not just a hookup. Then I'll let the conversation flow but I'll make sure that i'll stick with my decision and avoid any arguments. When the conversation and understanding is already okay, then that's the end. I won't go to any "friendship thingy" with him again either intimate or not because it will not do any good to me.