If it is a short bed there are 8 bolts to remove that you will easily find in the cross pieces of underside of bed. Disconnect hardware for gas filler and the ground wire. Then check for wires at back end of bed that connect to lighting etc. And disconnect wires. Then using a few strong people lift bed upward and have a spotter as you are lifting in case something is still connected. If all is clear then remove bed and set upside down on boards. If you wish to not remove it completely from truck set small boards on tires and bumper and set bed down. Make sure emergency brake is on so there is no rolling of truck.
