The four building blocks
Planets: what
Each planet stands for a function, a part of you with its own job. The Sun is identity and purpose; the Moon, emotional need and instinct. Mercury is how you think and speak, Venus what you love and value, Mars how you act. Jupiter describes growth, Saturn structure and what you master slowly, and the slow outer planets, Uranus, Neptune and Pluto, stand for change, imagination and depth. Counting the Sun and the Moon, as astrology does, makes ten planets. The wheel also shows the true north node and Black Moon Lilith, points rather than bodies (see the lunar nodes and Black Moon Lilith).
Signs: how
A sign is a 30° slice of the zodiac; twelve of them make the full 360°. A planet in a sign takes on that sign's manner, which comes from its element (fire, earth, air or water), its modality (cardinal, fixed or mutable) and its ruling planet. Mars in Aries, cardinal fire, acts at once; Mars in Taurus, fixed earth, starts slowly and then does not stop. Elements and modalities are the quickest way into any sign. Western astrology generally measures the signs from the March equinox, not from the constellations of the same names; tropical and sidereal zodiacs explains the difference.
Houses: where
The houses divide the sky over your birthplace into twelve areas of life. The first is you and your approach, the fourth home and roots, the seventh partnership, the tenth your direction and public role; the rest run from resources and communication to friendship and solitude. A planet's house shows where its function works hardest: Venus in the tenth may bring charm into working life, Venus in the fourth into the home. We use Placidus houses, and whole-sign houses beyond the polar circles (66.56° latitude), where Placidus cannot be drawn. The twelve houses covers each one.
Aspects: how the parts talk
Aspects are angles between planets, measured along the zodiac, and the classical ones divide the circle: the conjunction (together), the opposition (180°, half the circle), the trine (120°, a third), the square (90°, a quarter) and the sextile (60°, a sixth). An aspect links two functions, so it shows which parts of a person cooperate and which argue. The Moon trine Venus lets feeling and affection pass easily into each other; Mars square Saturn sets the urge to act against the demand for caution. An aspect counts only within a few degrees of exact, the orb, and the closer it is, the louder it speaks. Aspects describes each one and the orbs we use.
How to read the wheel
Four features orient you.
The horizon runs across the middle. Its left end, at nine o'clock, is the Ascendant: the degree of the zodiac rising in the east at your birth, which gives your rising sign. East is on the left because the chart is drawn as if you stood facing south, a northern-hemisphere convention that charts for southern births keep. The right end is the Descendant, the western horizon.
The houses count anticlockwise. The first house starts at the Ascendant and runs downwards. The numbers continue round the bottom to the seventh house, which begins at the Descendant, and over the top to the twelfth.
The Midheaven is near the top. It is where the zodiac crossed the meridian, its highest point in your sky, and it opens the tenth house. Because the zodiac is tilted, it is seldom at exactly twelve o'clock (more on the angles).
Above the line was the sky. Planets in houses seven to twelve were above the horizon when you were born, so a Sun there means a daytime birth. Through the day the sky turns past this frame clockwise: a planet rises at the Ascendant, culminates near the Midheaven and sets at the Descendant. A Sun in the twelfth house points to a birth soon after sunrise, a Sun in the seventh to the hours before sunset.
The whole zodiac passes the Ascendant once a day: twelve signs in a day, one every two hours on average. That is why the time matters so much, and why a chart without a birth time still shows a great deal without this frame.
A reading order for beginners
For a first reading, this order puts the loudest voices first.
1. The big three: Sun, Moon and rising sign
Your Sun sign describes identity and what you are working towards, your Moon sign your emotional needs, your rising sign your approach and the manner people meet first. When they share an element, the chart tends to feel of a piece; when they differ, expect someone who seems one person at work and another at home. The big three calculator finds all three.
2. The chart ruler
The planet that rules your rising sign is the chart ruler: Mars for Aries rising, Venus for Taurus, and so on. Traditions differ over three signs. Modern astrologers give Scorpio rising to Pluto, Aquarius to Uranus and Pisces to Neptune; traditional astrologers keep Mars, Saturn and Jupiter, and many readers look at both. The ruler's sign and house show where your whole approach is heading, and one voice among ten becomes a lead.
3. Mercury, Venus and Mars
The other personal planets fill in daily life: your Mercury sign how you think and talk, your Venus sign what attracts you and what you value, your Mars sign how you pursue what you want and what you do with anger. They often explain what the big three leave open, such as a gentle Pisces Sun that turns blunt in an argument. A Mars in Aries would do it.
4. The emphasis
Look for weight. A sign or house holding several planets, often called a stellium, marks an area of life the chart keeps returning to. Then weigh the elements and modalities: a chart heavy in earth tends to trust what it can touch, while one short of fire may need an outside spark to get going. Ten planets in twelve houses leave at least two houses empty. An empty house is read through the sign on its cusp and that sign's ruler; it is not a missing part of life.
5. The tightest aspects
Among the lines in the middle, look first for aspects close to exact, and for any that touch the Sun, the Moon or the Ascendant: these are the conversations a person lives with daily. A tight square between the Moon and Saturn says more than a loose trine between two outer planets.
6. Jupiter, Saturn and the outer planets
Jupiter and Saturn move slowly enough that classmates often share their signs, so read them through their house and their aspects: where you grow easily, where you learn the slow way. Saturn's cycle is also behind the Saturn return. Uranus, Neptune and Pluto stay in a sign for many years and describe a generation's backdrop. In your chart they become personal through their house and their contacts with your personal planets and angles.
A worked example
Take an invented chart: Leo rising, the Sun in Libra in the third house, the Moon in Capricorn in the sixth.
The big three. Leo rising gives a warm, visible approach: this person tends to walk into a room as if expected. The Sun in Libra aims at fairness and a life shared with others. The Moon in Capricorn needs something quieter: a firm hold on its feelings, a useful task, and time before it trusts.
The chart ruler. Leo is ruled by the Sun, so the Sun does double duty, as core identity and chart ruler. Its house turns the whole chart towards the third-house world of conversation, learning and neighbours; this is a chart that thinks out loud and likes company while it does. On the wheel, the Sun in the third house sits below the horizon, just past the lowest point, so this is a birth in the small hours.
The pull. Leo rising and the Libra Sun lean outwards, towards people and their good opinion. The Capricorn Moon, in the sixth house of daily work and routine, leans inwards, towards duty and self-reliance. Libra and Capricorn lie a quarter of the zodiac apart, and here the Sun and Moon form a close square. A beginner wants to decide which one is the real person. A reader keeps both: someone who is the easiest company at a gathering and then goes home to check tomorrow's list, who charms quickly and trusts slowly. The friction between pleasing others and relying on no one also supplies drive. The Moon gives the Sun's charm staying power; the Sun draws the Moon out of its workroom.
Common mistakes
Reading each placement alone as a verdict. "Moon in Scorpio means jealous" is a sentence about one placement in a chart of many. Each piece is shaped by its house, its aspects and the rest of the chart.
Treating squares as bad. Squares and oppositions describe friction, and friction produces effort. Trines describe ease, and ease can go unused. A chart full of trines is not a better chart.
Forgetting that the time decides the frame. The rising sign, the Midheaven and the houses depend on the birth time and place, and a guessed hour gives a confident-looking chart with the wrong frame. If you are unsure, look for the record first, or read the chart without houses.
Judging a person by the Sun sign. The Sun is one planet of ten. Two people with the same Sun sign and different Moons and rising signs can be very unalike. If you were born around the day the Sun changes sign, check which side yours fell on (born on the cusp).
What a chart cannot tell you
We read a birth chart as a description of temperament: what a person leans towards and needs, what comes easily, where they tend to struggle. It does not describe events or set a fate: what happens to you depends on choices and circumstances. Twins born minutes apart share almost the same chart and still grow into two distinct people.
Where to go next
Next, read the houses and the aspects, then the angles. Retrograde planets explains what it means when a planet was retrograde at your birth, which is common and no flaw, and the birth Moon phase covers the phase our free chart names. Synastry shows how two charts are compared. If another site gives you a different chart, why birth charts differ goes through the usual causes.