Keep in mind there are two types of LORs -- those for the SAs and those for the MOC noms. WRT SAs, I can only speak to USNA. They don't want LORs in the traditional sense. Rather, USNA sends an email link with a form they want the junior year teachers of math and English to complete. I suggest talking to your teachers now to let them know how important this is to you, etc.
Each MOC has his / her own requirements for LORs, including number permitted, who they want to complete them, etc. Whether these should be specific to a SA is a complex question. The easy answer is "yes," -- each should be personalized to a particular MOC and to a particular SA. That said, if you apply to the 4 SAs that require noms and request noms from 3 MOCs, and use the same recommenders, this quickly gets out of hand. Adding to the complexity is that some MOCs make you rank the SAs or even choose among them. Thus, if your choice is USNA (or it's first in your ranking), sending a letter about how you'd make a great Army officer will seem a bit odd.
Thus, each candidate needs to think through the process. What are the "mandatory" LORs (where you don't get to choose who completes the recommendation)? How many SAs are you applying to? How many recommenders will you use? Does the MOC require separate LORs for each SA to which you're applying (hopefully not)? How strongly do you want one SA over the other (where you might really want to personalize)? How much of a burden are you putting on individual recommenders -- how many different LORs is each being asked to write?
The most important thing in any LOR is specificity. Consider the following: "Mary is an exceptionally intelligent and motivated student who drives every project she touches to a successful conclusion." Sounds great, right? Not really. It's a bunch of nice words strung together.
The following makes it A LOT better: "For example, Mary took charge of the junior class prom project, which was foundering, only three weeks before the event. When she took over, there was no venue, no band, and no plan. Mary quickly found a unique venue -- a remodeled bus station -- at a bargain price and decided on a Caribbean theme. She put together a team of juniors and seniors and held daily meetings to make sure all deadlines were met and the project came in under budget. Under her leadership, they found a reggae band, arranged for catering from a local minority-owned business, and spend an entire day decorating the venue. I was one of the chaperones and can tell you that this was the most successful prom in the fifteen years I've been at Downtown High School. It was possible only due to Mary's strong leadership, drive and creative thinking."
Hopefully, your recommenders will know / remember enough about you to include specifics. If you're not sure, don't be afraid to provide them a "cheat sheet" of your accomplishments. Think of them in terms of the above . . . not just what positions you've held, but specific things you've done -- how you have led things, made them better, etc. Also, when you have a choice in recommenders, pick those who write well / effectively and meet deadlines.
