On my 17, for the wing sockets, I take small rags and stuff them in the upper section of the tube (the idea being that if a small amount of water gets in, it will be absorbed by the rags and not pool in the bottom of the tube). Then I stick the wing socket plugs in, and I tape a piece of plastic sheet (garbage bag) over the wing socket. And last, I put the cover on the boat. Haven't had any issues doing it this way. Other folks have recommended simply pouring some anti-freeze in the tube.
I leave the centerboards in the hulls, but will either leave the centerboards in the "down" position, or remove the spring completely. The idea being that you want to relieve the spring pressure.
I think with the one-piece and two-piece tramps, you have to disassemble the boat to remove them.