For the inset square-head plugs: smaller ones are 3/8 or 1/2 inch and your ratchet handle or extender will fit; bigger ones take bigger ratchet tools (expensive if you don't have them) or, alternatively, go to your local hardware store and find a pipe plug with a "male" square-head on it to match your recessed square-head, stick them together, and turn using a pipewrench on the pipe plug.
Lots of info in the archives and some recent posts regarding your wobble in road gear, it's a common problem.
