This is great advise, TBO. After completing my active duty service (4 years) and after graduating from college and acquiring my master's degree, I wanted to return to the reserves and sought an OCS selection.
I purchased a book on the written OCS test and went through it from cover to cover 3 times. When I took the test, some of the questions were identical to one's in the preparation book. I aced the test and it makes a huge difference in choice of career field.
Although I served in a different branch of the military, all of the Marines I have known and worked with are quality people. Based on my experience, "The Few, the Proud, The Marines" is an accurate description.
Good luck!
EODGUY