Let's say I have 90 minutes to study and am essentially an advanced beginner... what do you think is the best way-- specifically-- to spend that time?

Sorry if you've heard this before but most people agree about 90% working on tactics puzzles, possibly then spend the rest on Endgames, a tiny amount on opening principles and a few simple lines. Strategy shouldn't matter at this stage..

www.chess.com/chessmentor

www.chess.com/tactics

:)

i agree with atomichiken tactics, tactics,tactics

Assuming you have the basics for 2 openings with white and 2 whith black, then work on tactics...tactics..tactics...

What about playing over annotate games? That seems to be highly recommended... and I'm not sure of the best way to make that study meaningful...

I know it's a bit late, however Capablancas Chess fundamentals helped me alot (it can be found on the internet for free) and play chess 960 that way you get past the book moves, and only talent is appreciated.