The predictive side of astrology uses what is known as progressions to map out long term trends in the individual and transits to map out short term as well as long term events (when using the outermost planets).
Transits:
Nobody has any arguments with the transits. They are the actual day to day movements of the planetary bodies and how they affect your natal positions by expecting them. The Moon, moving 12 degrees per day, is the minute handle on the clock, and is an excellent timing or setting off mechanism for activating your natal, progressed, or slower transiting planets. The Moon has the greatest sway over our daily activities and anyone with planets in Cancer or Capricorn will be especially sensitive to its transits.
The transiting Sun, Mercury, Venus, and Mars move from one to two degrees per day (except for retrograde movement) and range from being daily to weekly influences over individuals and events. The Sun spotlights whatever planet it aspects (especially by degree) and anyone with planets in Leo is especially sensitive to its influence. Mercury transits affect all forms of communication, work, and transport, and are especially powerful in the lives of those who have Gemini or Virgo emphasized in their charts. Venus transits affect all activities having to do with pleasure, socializing, and money and has a particularly strong sway over individuals with Taurus and to a lesser extent Libra in their charts. Mars transits stimulate activity of all kinds, but especially sports and sex and sometimes even war and violence. People with planets in Aries and to a lesser degree Scorpio are especially sensitive to the transits or movements of Mars.
The transits of the outer planets from Jupiter to Pluto are much slower and have longer term influences. Jupiter opens doors and opportunities and stimulates growth and expansion and is especially powerful in the lives of those who have Sagittarius emphasized and to a lesser extent Pisces. Saturn tests, restricts, and solidifies, and sets limits or boundaries and is especially powerful in the lives of those with Capricorn emphasized in their chart and to a lesser extent Aquarius.
The three outermost planets move very slowly so that their transits over any planet in your chart are powerfully and deeply felt. Uranus shocks, surprises, liberates, originates, and reverses, and is powerful in the lives of those who have Aquarius emphasized in their chart. Neptune confuses, sensitizes, deludes, soothes, and intoxicates, and is powerful in the lives of those with Pisces emphasized in their chart. Pluto emphasizes, deepens, obsesses, intensifies, destroys, eliminates, and rebuilds, and is powerful in the lives of those with Scorpio emphasized in their chart.
Progressions:
Progressions work on a "day for a year" basis and reflect an inner enfoldment which you make happen in your outer life.
There are two main methods of progressing your planetary positions; one is to count every day from your birth as one year and see where the planets have moved. This means, for example, that the 30th day from your birthday will show what is to happen on your 30th year of life. In this method the inner planets, especially the Moon will show definite changes, whereas the planets from Jupiter to Pluto will show very little change.
The other method, which is simpler and more beautiful, is to take your planetary positions as they are, to the degree and minute, and project them into the future using the "one degree equals one year" method. If your natal Sun is at 2 degrees Aries, for example, when you are thirty years old it will be at 2 degrees Taurus. When the Sun or any planet progresses into a new sign, you will begin to acquire some of the characteristics of that new sign, but it will never overpower your original placement -it will just enhance or modify it.
We are continually growing and changing, and progressions are the indicator of this. To experience all of the progressions in your chart you must live to be at least 360 years old, which is a real rarity these days.