Writing horoscopes requires a little research. As part of my preparation for writing annual stars, I typically create an astro wheel that covers all the planetary movements for the year ahead.
The 2013 version is to the left. In addition, I write up all the main planet aspects on a couple of extra pages.
This gives me the raw data of the astro highlights for the year ahead, which I turn into horoscopes. 
It’s all a bit magical, but definitely a little more data based than you might think horoscope writing to be.
Since there’s so much focus on Mercury at the moment, I thought I’d share Mercury’s peak dates for the year. This covers Mercury aspects to other planets. For Mercury retro info, pop over here.
In 2013, Mercury meets up with other planets as follows:
– Mercury/Pluto, January 6 + December 30 (Capricorn)
– Mercury/Neptune, February 6 (Pisces)
– Mercury/Uranus, April 19 (Aries)
– Mercury/South Node, May 9 (Taurus)
– Mercury/Jupiter, May 27 (Gemini)
– Mercury/North Node, October 5, November 3 + 18 (Scorpio)
-Mercury/Saturn, October 7 + 29, November 26 (Scorpio)