In modern life, astrology is best used not to predict the future as if it is unchangeable and can be clearly viewed but to understand where you are in the process of your soul's evolution: what lessons are coming up for you now and what catalysts might you find cropping up that help you address the current issues your soul is ready to learn?
There are several other techniques that can be used in the realm of predictive astrology. Transits, secondary progressions, solar arcs, directions (also known as primary progressions) -- their methods differ but their commonality is that they are all techniques designed to understand the evolution of the natal chart which is your soul's evolution. They all show influences that act on your birth chart over the course of your life. These techniques all represent a way to take the natal issues that you are learning your whole life and understand the pieces that you might be learning at any given moment. By analyzing the influences on your chart currently, we can gain more insight into what the point is of the current lesson, which can give understanding in times of confusion; hope and strength in times of depression and frustration.
One technique that most every astrologer uses is to analyze the transits that are affecting your chart. Your natal chart is a map of the sky when you were born. It's as if the planets are frozen in time at the exact moment of your birth. However, while your personal map is frozen, the actual planets in the sky continue to move. The planets are said to 'transit' around the sky, and as they do, we can see how they might interact with the frozen planets in our natal chart. Transits are the actual current movement of a planet at any moment.
Most other predictive techniques are based on symbolic planetary movement. While the transiting planets are literal (where is Pluto actually in the sky right now?), there are techniques for symbolically moving planets around your chart to represent the evolution of your chart. The chart is progressed using the symbolism of a day for a year. So the actual movement of a planet in a day represents 1 year in your life. If the sun moves about a degree a day, then in secondary progression techniques, it moves forward 1 degree forward every year you are alive from where it started in your natal chart.
In the book The Changing Sky by Steven Forrest, he gives the example of dog years. Most of us would understand what someone meant if they were to say that Fluffy is the age equivalent to 70 human years. In actual years, she is probably 10 years old. But in popular reference, we understand 7 'dog years' to equal 1 actual year on Earth. It is the same principle here. 1 actual day represents 1 year, symbolically.
Solar Arcs are also progressions, but instead of progressing each planet according to it's own natural movement, every planet is progressed according to the sun's movement. For example: the sun moves about a degree a day. The moon moves about 12-14 degrees in a day. With regular secondary progressions, the sun would move a degree per year, and the moon would move 12-14 degrees per year. However, with solar arcs, every planet moves 1 degree per year, according to the sun's motion.
The solar return is a chart not based on where all the planets were when you were born (such as the natal chart), but a chart based on the moment each year when the sun returns to the place it was when you were born. Since the sun's position is not exactly the same from calender year to calendar year, this is not necessarily a chart for the day and time of your birth. It is also generally calculated for your current location (though not always), regardless of your birthplace.
The solar return does not replace your natal chart nor does it supersede it's importance. Every chart that is drawn up for you must always answer to the natal chart, for that is the baseline of your life. However, a solar return can tell you what themes are of predominant importance for you in the upcoming year (from one birthday to the next, basically). It can be used in conjunction with transits & progressions to give you a look at what the next year of your life may entail.
Predictive Astrology in Action
Let's say that our Mars is in the sign of Pisces in the 1st house. A person with the Mars in Pisces in the 1st house would be learning to defend the territory of self, to direct their will out into the world and make their personal strength visible to the world. They would do this through the method of Pisces which is gentle, compassionate, and open. They would also be vulnerable to their sense of self being attacked if they are too yielding and begin to utilize the method of dark Pisces: being too self-sacrificing and submissive without need. Their method will never be one that is fierce or antagonistic, because that is not the way of Pisces, but they will, through gentle means, need to learn to assert themselves in the world, to make their will known and visible to the world.
Now, let's say that transiting Uranus comes and lights up that Mars in Pisces in the 1st house place in us by forming a conjunction (in the same place as) to our natal Mars. So that martial lesson comes to the forefront of our lives. We have to understand what the planet Uranus represents itself, and we also have to understand what Mars in Pisces in the 1st house means to us as part of our natal life lessons. Transiting Uranus would bring with it circumstances that might shake us up, that might be chaotic. There may be something in our situations in the world that is changing rapidly. In a sense, the circumstances don't matter as much as the point behind them; what they are trying to teach or get you to discover. What transiting Uranus is trying to get us to ask ourselves is 'have we let ourselves fall asleep here? Have we fallen into behaviors that are not authentic in this area of our life?' If so, Uranus wants to wake us up, and it'll do so by bringing rapid change and filling us with a feeling of being electrified. The person with Mars in Pisces in the 1st house might find that they have been too accomodating for too long and their own identity has started to slowly disappear. Have they been giving to others authentically through compassion as Pisces asks and thereby gaining a more powerful sense of self? Or have they been giving out of a sense of martyrdom and losing themselves in the process? They can use this Uranian time of reawakening to get back in touch with what that lesson is all about, and starting letting their will be known again, even if it is likely to cause upheaval in their world and relationships (since the world has probably gotten used to their behavior being more accomodating and complacent).
Always, an important point to mention is that the natal chart is our baseline. The current planetary impact on our natal chart cannot give us any insight that we couldn't trace back to our understanding of the natal chart. Current planetary movements help us to understand the timing of the lessons in our lives. It is a way to break down the larger natal lessons into smaller and more easily understood (hopefully!) chunks. Everything we are going through right now according to the current planetary movements will always tie back to and enlighten us about our own natal, lifelong lessons.
*Secondary progressions are called 'secondary' because primary progressions or 'directions' came first. The basic difference between the two methods is the math behind the movement of the progressed planets. This method is rather complex and is not frequently used.