Being an old prior enlisted guy, I never thought about anything other than Alphas. I came from the boat school, so I had my full complement of uniforms upon comissioning. I checked into TBS in Alphas (the way I was taught back in '92 as a PFC). I was told to check into MATSG in Charlies, but again, old habits die hard and I checked in wearing Alphas. At the boat school, we used to say "you can always dress up". No one will laugh at you if you're wearing Alphas, because you are doing the correct thing. Especially for the young enlisted guys who see you.
According to the Marine Officer's Guide, you should put on your best civilian clothes (or Service A if you prefer), get a haircut, and go to the base the day prior to your orders. Go to the adjutant's office (or SDO of the squadron you're checking in to), and introduce yourself, and ask the pertinents (when, where, and what uniform). I wish I had done that with my first squadron, as I sat around from 0730-1400 waiting for the XO (because he was on the night schedule). Had I done what the Marine Officer's guide suggested, I would have checked in at 1400...
