Military Ranks

Like many things in Star Wars, many military things don't quite make sense. Rank structures are one of those things.

Rank for officers, in ascending order, is Lieutenant, Captain, Major, Commander, Colonel, General for ground forces or Admiral for naval forces. Traditionally, commander is a naval rank and lower than captain. Colonel is an army rank equal to naval captain. Going off many of the Expanded Universe books, particularly the X-Wing series, there is also a Flight Officer rank below Lieutenant, which is could be equal to a Warrant Officer.
I'm going to to go with Flight Officer/Second Lieutenant, First Lieutenant, Captain, Major, Commander, Colonel, General/Admiral. Imperial forces use Ensign, Lieutenant, etc.