I would say anywhere that it won't get bound up and isn't connected to the hitch itself...the reason being that if the hitch failed for some reason the cable might not pull. Someplace attached directly to the truck frame is probably best and I used to have a clip fixed into my last TV for that purpose. I haven't done it to my new one yet, so I'm just tying it to my chain brackets on my hitch for the time being by unplugging it, then running the loop through the bracket then passing the other end through the loop and plugging it back in.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition