12 Volt power source when truck is on

hey i just bagged my 2004 f150 heratige and i was wondering where you guys run your 12 volt wire from that only is hot when the truck is on. I have a switch now, but i forget to turn it off at night sometimes, my tank dont leak, but i just dont want to have to turn it off and on all the time. Someone told me my radio, but i know that wont work cause its always hot cause even when the trucks off the red light flashes. Maybe run it from the ATT blue wire? Someone help me out. PS Fuse box dont work either...