My opinion:
ONLY way is to mount on a quick attach, such as a truck hitch. Well, 99% of the time anyway. Mount it on a 2 inch drawbar and mount a 2 inch receiver at the front of your trailer (and anywhere else a winch would be handy like rear of trailer, front of truck, rear of truck, front of garage bay attached to floor, or rigged up with chain to anything).
Pros: Gets it out of the salt/road shit/etc. Protects from theft, and makes it more versatile. You can also remove it when it's in the way of something on your trailer.
Use Anderson connectors and butcher a set of jumper cables by cutting near one set of clamps and splice back together with Anderson connectors, then you can use them to connect winch to battery with the battery sitting beside the winch (short half of jumpers) or connect to tow vehicle battery with the long half of the jumper cables.
Edit: Now that I've read the whole thread, that's Nine recommendations for a multi mount.