The monthly horoscopes utilize the planets Sun, Mercury, Venus and Mars predominantly to determine the effects on your Sun sign. If you have an exact the time personal horoscope can be drawn up and these transits and then looked at with respect to the rising sign at a time you are born. In Western astrology both the Sun sign astrology and rising sun astrology a given validity. Vedic astrologers calculate the transits with respect to the lunar position more than the rising sign.
Many astrologers base transits on the movements of the Sun to different houses of your horoscope (to see the Houses of the Zodiac click here), usually by studying month by month where the Sun will be, we can gain an insight into the upcoming trends fairly accurately. These transits of the inner planets when making contact with the other planets will obviously trigger the more important events and this is how we can forecast what and when the important highlights of the year will occur for each star sign.