What was different about the practice used for the battle of trafalgar?

The Royal Navy was counting upon the poor and inexperienced French/Spanish crewmen when engaged by the better trained British crewmen when fighting cannon to cannon when their sailing ships rode up along side each other. Plus, Admiral Nelson of the British (Royal Navy) had engineered a stronger method of "command and control", that of line ahead movement, in which each vessel of his fleet could see his flag signals from his "flag ship."