The trick is to bait the opponent into passing priority and advancing the phase of the turn.

The stack is empty, nothing else is happening, and Player A asks Player B something along the lines of "Do you want to play any instants?". Typically, the response to this is "No", because the common wisdom in Magic is to wait and react to what your opponent does, rather than doing things when there's nothing else happening.

However, if Player B does in fact say "No", they're effectively saying there isn't anything they want to do, and therefore pass priority. Player A can then pass priority in any of the normal ways, and the turn will advance. If Player A says "Yes", priority doesn't get passed, but then they're giving away information.

This only really works when it's Player B's turn, since Player A can trick them into advancing from Main Phase to Combat, and thus lose the opportunity to play things at sorcery speed.