Decant leaving enough liquid (2 or 3 times the thickness of the yeast layer) to swirl up the yeast easily, then once all the yeast is unstuck from the bottom of the jug or whatever, straight in it goes! Just make sure you refrigerate long enough (not just overnight, but several days) to settle ALL the yeast. You don't want to leave the least flocculent cells in the liquid you discard, or you may not fully attenuate or reduce diacetyl, etc. [This is a bigger concern if you repitch for the next batch because over generations you'll be selecting only the most flocculent cells.] You don't need to worry about the yeast being refrigerated for days and days, and don't warm up the starter before decanting and pitching: as soon as it's pitched into the relatively warmer wort it'll wake right up!