Most western astrologers look to the aspects(by degree) when determining whether a planet is good or bad in the chart. They count the number of good aspects(most trines and sextiles and sometimes the conjunction) versus the bad aspects(most squares, oppositions, quincunxes, and sometimes the conjunction). They also look to the sign or house it's in, and if it's retrograde or not.

The sign or element a planet is in, is in my opinion, by far the most important consideration, and this is highly dependant on the rulership scheme in astrology. Because the planet rulership or dignity issue has not been completely resolved, there will always be some contention as to which planet is best placed in which sign.

This is no problem with the Sun and Moon which have always ruled one sign each(Leo and Cancer respectively), so that the Sun is always best placed in Leo or a fire sign and the Moon is always best placed in Cancer or a water sign. Next best are Sun in air and Moon in Earth because of the element compatibility. The exaltations of the Sun(Aries) and Moon(Taurus) confirm this harmony.

The problem is with the other five traditional planets which have for thousands of years ruled two signs each; Gemini and Virgo for Mercury, Taurus and Libra for Venus, Aries and Scorpio for Mars, Sagittarius and Pisces for Jupiter, and Capricorn and Aquarius for Saturn.

With this double rulership scheme, it's difficult, other than through observation, to determine which element or sign any of these planets works best through. The exaltation scheme offers some help, but even here there is no complete consensus. It is still undecided, for example, as to whether Mercury is exalted in Virgo or Aquarius.

Thankfully, in the last quarter century, the discovery of new planets has clarified some of the ambiguity of the double rulership scheme. With Uranus(discovered in 1781) as the true ruler of air sign Aquarius, Saturn is best in Capricorn or Earth. With Neptune(discovered in 1846) as the true ruler of water sign Pisces, Jupiter is best in Sagittarius or fire. And with Pluto(discovered in 1930) ruling Scorpio, Mars is best in Aries or fire. The opposing element of a planet is also good but less so than the home element. Study and observation will bear out these conclusions.

We are left with Mercury and Venus still supposedly ruling two signs each. Most will say that Mercury is best suited to Gemini and Venus to Libra, but I disagree with the latter. In my observations, Venus is best in earth or water. The exaltation of Venus(Pisces) strengthens this conclusion. Mercury is a real puzzle; I can see both the Gemini and Virgo influence there, but edging more to Gemini. For me, the Ascendant(Earth) does best in Libra or air but also in fire.

Well-placed planets by sign or element produce favorable characteristics in the native, and the more you have of them, the better. This does not mean that someone with a majority of planets unfavorably placed will necessarily be "bad". Other factors such as education and proper upbringing can mitigate this, but it is true that he or she will need to exert more effort to be "good" or successful.

In my opinion, the world is in shambles because most of the "bad" planet placements in astrology have been allowed to run rampant. That's as far as I'll say without stepping on too many toes. Supposedly there was a time when the planets(archangels) were fixed in their home signs and all was well, but ever since they began "wandering" and going into other signs, trouble began.

For a society that goes pretty much on looks or face value, having a well-placed Ascendant(in air or fire) can go a long way, especially for women. Most models or good-looking people have masculine Ascendants. For men, substance, skill, or professionalism is more critical, and a well-placed Moon(in water or earth) is invaluable. Masculine Moons can be rather crude or insensitive when compared to their feminine counterpats.

For speaking and thinking clearly or effectively, a well-placed Mercury(air or fire) is best. Feminine Mercurys are much too quiet or sensitive to get their views across publicly, unless it's done through writing or internet. For class, taste, and appreciation of the good things in life, Venus in earth or water is best. Masculine Venus signs can come across as being too coarse(fire) or impractical(air).

For energy and getting things done quickly and fearlessly there's nothing like a good Mars(in fire or air). Mars in fire in particular will be good for staying active and positive. Mars in air is more for intellectual or social activity. Feminine Mars signs will be much slower or less active and lack drive or confidence. For higher learning, travel, or doing good deeds, a well-placed Jupiter(especially fire) will be best. Feminine Jupiters can more easily fall from grace than their masculine counterparts.

For planning, organization, responsibility, and common sense, a well-placed Saturn(earth or water) is best. Feminine Saturns tend to lack realism, structure, and grounding. For positive innovation, change, or liberating truth, Uranus in air or fire is best. Feminine Uranus signs can be weird or negatively disruptive.

For fine sensitivity, artistry, and idealism, Neptune in water or earth is best. Masculine Neptune signs can be too insensitive or impractical. For being deep, decisive, and instinctual, Pluto in water or earth is best. Masculine Pluto signs can be overly extreme, selective, or obsessive.