Others have pretty well covered it.
If you have neither an air compressor available to blow the lines out with (at relatively low pressures) nor a winterize inlet port to pump antifreeze in, you can also pump antifreeze by putting some in the previously emptied fresh water tank and pumping it around from there. That's not the preferred method--it takes a good bit more antifreeze, and equally more work to clean it out in the spring--but on a few trailers it's about the only way they make a provision for.
If you have a washing machine, consult its instructions for proper winterizing. If you have a water filter spigot on the kitchen sink or something similar, typically they need to be removed/disassembled and the housing drained.
Don't also neglect to remove foods (that attract critters) and water-based cleaning products etc. that can freeze and burst their containers.