In all of my beginner's Astrology teleconference classes, I teach my students how important it is to thoroughly analyze the Sun, Moon, and Ascendant (or Rising sign) of any horoscope.
The signs explained
The Sun sign represents your basic essence and vitality. It's how you experience your ego, and the traits in your Sun sign speak to qualities you're learning to embody.
The Moon sign represents your emotional nature and the feeling instinct. It's how you experience nourishment and safety. It's what you need to feel fulfilled.
The Ascendant is what I like to call the "cover of your book." It reveals the qualities you most visibly show to others upon first impression. While this cover is definitely not the entire story, it does provide significant information about how you approach your world.
It's very easy to put together some sentences with keywords from each sign that allows you to uncover anyone's cosmic trinity. Let's use the following as an example to illustrate the simplicity.
Let's say someone's Sun is in Taurus, their Moon is in Sagittarius, and they have an Aries Rising. Without knowing anything else about this chart, you can surmise the following.
Sun in Taurus: This person has the energy to be practical, grounded, and sensual, and to use his or her talents to create something lasting. They radiate warmth and vitality when their physical and material security needs are met.
Moon in Sagittarius: He or she has the need to spread their wisdom and to have their philosophy listened to and respected. They need to teach and learn in order to feel secure and fulfilled. Travel, higher learning, and metaphysical pursuits will help them feel nourished.
Aries Rising: The cover of this person's book is energetic and enthusiastic. They come across as independent, courageous, and pioneering. They show others that their a leader and willing to take the initiative in order to express the energy of their Sun sign and fulfill the needs of their Moon sign.
It's that simple! Now, following the same format, I encourage you to do this for yourself and anyone else you're curious about.