Our property has an existing 5' wide x 12' long dock. It is basic 2x6 4 stringer frame with 5/4 decking. Steel poles with auger points secure it. We have 3' thick muck bottom so the points will be screwed into the solid earth beneath.
I just picked up lumber to add another 5'x12' section plus a 6'x14' added to the end to make an L shape.
I ordered my brackets from DH docks in MN. They are a nice interlocking hook design that also ties the corners together. Pipe poles through adjustable brackets.
We plan to build the frames and then drag down to the lake and assemble during late ice season.
I also ordered one X brace for good measures, but I think that the L shape should help a bunch with sway.
http://www.dhdocks.com/lakesideliving/index.php?main_page=index&cPath=60 
