Mercury (communication and information) enters Sagittarius on December 4th. That means more information, bigger promises, expansive thoughts.
This is great if you're looking for inspiration, or something to boost you out of a mental rut. Mercury's square to Neptune at 2 degrees Pisces (from December 4th to December 6th) can be especially lovely; here is idealistic, dream-weaver energy that floats above the petty, annoying details. Enjoy, but take all promises (for these two days) with a grain of salt. And watch what you promise others. If you have planets/angles from 2-3 degrees Pisces or Sag, pay close attention to all your conversations/phone calls/emails; it will be easy to overlook certain details.
The affairs of the Sagittarius area of your chart (which is already being transited by the Sun) will be put into words. For some, this could manifest as a rush of outside contacts. For others, private insights may surge up and out. This is not about getting it perfect, or nailing down every word. Sagittarius is the sign of exploration. It's Mutable Fire; shifting, grabbing new ideas, burning with enthusiasm, then moving on. Everything is interesting, so keep your mind (and inbox) open.
Mercury's transit of Sag will last until December 24th.