Continuity mistake: Near the beginning of the episode, Will is pouring some wine. First, he pours a full glass and hands it to Grace, then he begins to pour another glass that obviously already has wine in it. He then hands this to Grace and takes an empty glass from her to fill, which he already filled (there is no sign that she already drank the wine in the glass).
Continuity mistake: When Will and his date are having dinner at Will's flat, will pours his date a glass of wine into an empty glass that the date is holding out. When the shot changes the date is holding a full glass near his chest, and when the shot changes again, Will is still filling it up.