Astrology is just a bunch of poopity poo.
We all love to read the astrology section in the backs of magazines or newspapers. Some people, like my friend Alexandra, are hardcore astrology people. But, I think we can all agree that we really can't trust astrology.
After all, astrologists are not scientists. Astronomers are the real scientists. Astrology operates on the movements of the sun and stars, which can be used to predict the future.
However, there is no force, known or unknown, that could possibly affect us here on Earth the way astrologers claim. Known forces weaken too fast, letting one source utterly dominate (the Moon for gravity, the Sun for electromagnetism). An unknown force would allow asteroids and extrasolar planets to totally overwhelm the nearby planets. At best, the gravity from the planets in our solar system is a tiny fraction of the Moon's. So if gravity were the force behind astrology, then the Moon would dominate all the planets combined. Yet it doesn't in any astrologer's horoscope.
Astronomers have now found about 150 planets orbiting other stars. These are very distant, certainly, but hey! Distance is no issue. So therefore these planets must affect us too. Now, these are only the planets we've discovered so far. Given how many we've found, and what kind of stars they tend to orbit, it's reasonable to assume that there are billions (billions!) of such planets in our galaxy alone. They're everywhere! Why don't astrologers include them in their horoscopes?
Astrologers tend to rely on our ability to remember hits and forget misses. Even an accurate prediction may be simple chance.
Study after study has shown that claims and predictions made by astrologers have no merit. They are indistinguishable from chance, which means astrologers cannot claim to have some ability to predict your life's path.
There is harm, real harm, in astrology. It weakens further people's ability to rationally look at the world, an ability we need now more than ever.
If you further wish to look at how astrology is just a bunch of poopity poo:
The Skeptic Dictionary's entry on astrology