Memorize the unoffical 12th General Order as well...
To walk my post from flank to flank, and not take sh*t from any rank. 
As far as rank structure its pretty much a matter of repetition and counting stipes and stars. Go over it enough and eventually you'll memorize it. First memorize what order the ranks come in. Once you have that down (fairly easy), memorize rank insignia.
The first 3 ranks are non-rates, or non-NCOs. Seaman Recruits (E-1) have no rank insignia. A Seamen Apprentice (E-2) has 2 stripes and a Seaman (E-3) 3 stripes. Fairly easy, just count the stripes. Stripes for non-rates are straight.
Once you get to the Petty Officer ranks (NCOs), rank insignia has upside down V shaped stripes, and rockers as you move higher up the chain. A Petty Officer Third Class (E-4) has one upside down stipe w/ an Eagle above it. A Pretty Officer Second Class (E-5) and a Petty Officer First Class (E-6) resemble a Petty Officer Third Class, except 2 and 3 stripes respectively.
Once you get to the Chiefs, you start seeing rockers and stars. A rocker is the rounded half-moon looking "stripe" on top of the rank insignia. All of the Chief rank insignias have one rocker, 3 stripes and look very similar except for the stars. A Chief (E-7) has none. A Senior Chief (E-8) has one, a Master Chief (E-9) has two. The Master Chief Petty Officer of the Navy (E-9) is the senior enlisted man in the entire Navy, and has 3 stars at the top. He also has a star in between the stripes and rocker. All other Chief rank insignias have an anchor in place of that star.
With the Commissioned Officer ranks just remember that silver outranks gold in the cases of similar insignia on the collar. So if you saw two naval officers standing beside one another, both wearing oak leaf clusters, one silver and one gold, the silver is the Commander (O-5) and senior. (a gold oak leaf is a Lt Commander)
The Warrant Officer ranks are fairly easy. 3 blue squares in a gold field on the collar is a W-2, 2 blue squares in silver field is a W-3, and 3 blue squares in a silver field is a W-4. All are called Chief Warrant Officers.
First memorize the collar devices for the officers, then memorize the epaulets.
The American Marine Division has the highest combat effectiveness in the American armed forces. It seems not enough for our four divisions to surround and annihilate its two regiments.
---Mao Tse Sung to General Song, prior to Chosin Reservoir
