Nothing much to it, since the detritus doesn't seep into sand as it does on gravel, just hover your siphon at about an inch or so, it'll pick up the trash without disturbing the sand too much, if at all. If you pick up some by accident simply pinch the hose to slow the current and the sand will float right back down.
If you have a hard time seeing where things are, once you lower the water (for the change) use your hand to gently agitate the surface right above the sand (say an inch or two above it) and you'll see the muck move around. Let it settle and vacuum as described above.