I've just gotten to the point where I can identify (to some degree) the # grain line for river condition when fishing sinking tips, but with lakes and still water, its a whole different ball game, first and foremost because a line has less friction than in a flowing river, and can sink faster and longer.
Can you (still water fly fisherman) possibly outline some conditions coordinated with the type of lines you would use? And, also where the fish would be under those conditions? This could be ridiculous since I'm sure a book could be written about any facet of this.