Aries
Mercury in Aries is quick to jump to conclusions, they can be verbally abusive. Where Mercury in Sagittarius is sarcastic, in Aries it's mean. These are quick thinkers in an emergency but have short attention spans.

Taurus
Mercury in Taurus are great with numbers, they do very well in accounting or as bankers and have a very mathematical mind.

Gemini
Mercury in Gemini, the mind that never sleeps they are constantly thinking, sometimes manifesting the things they think, but usually ends up in worry. Their thoughts flip from thing to thing making it hard to focus. Writing is good for them, makes them focus, these people do best when they make lists. Gemini is ruled by the Mercury so mercury works well here.

Cancer
Mercury in Cancer expresses with emotions. They are compassionate, sensitive and moody these are the folks who talk to their plants . Those with mercury in cancer like to give motherly advice.

Leo
(Fall)
Mercury in Leo is often heard before seen, they are dramatic. This is a fixed sign and like all fixed sign mercury's they are stubborn. They like to lead and are braggers only second to mercury in Sagittarius Leo is the fall of mercury and the worst possible placement for the mercury, the energies are terrible together exhibit the bad side of pride and ego.

Virgo
Mercury in Virgo has an excellent mind for details. They are content to stay in the background being painfully shy and insecure. Mercury in Virgo is also interested in health. They can get to bogged down with details and cant see the forest for the trees. Virgo is ruled by the Mercury so mercury works well here.

Libra
Mercury in Libra must have balance in life. These are the people who like to only see the pleasant things in life, don't like life's deformities or want to acknowledge the homeless, not much depth to their thinking and they can be very indecisive. They would be great at running an art gallery full of beautiful things.

Scorpio
Mercury in Scorpio are deep thinkers, you are never quite sure what they are thinking. They have an intense mind and go at things with a single minded drive, they make great researchers. Just don't forget about Scorpios manipulation and control issues.

Sagittarius
(Detriment)
Mercury in Sagittarius is sarcastic, these are the braggers, they want you to think that the sags are painfully honest, but it is not true... they are just blunt and rude. They are philosophical and like college and higher learning, it makes them feel important and knowledgeable. They present a worldly image but Sagittarius energy only skims the surface, they don't know a lot about anything but they want you to think they know it all.

Capricorn
Mercury in Capricorn are the most serious minded of the zodiac, not much sense of humor here. They can be depressed, pessimistic, reliable, responsible, dependable practical and dull. You can count on the Capricorn in mercury to bring you right down to reality. This sign needs scheduling nothing is done impulsively

Aquarius
(Exalted)
Mercury in Aquarius the inventors of the zodiac, these are the guys that work at NASA they can be very weird... like seeing UFOs or being abducted . They are very clever, these are the minds that make our lives easier thinking of new things like microwaves. Mercury is Exalted in Aquarius so the energies work well together.

Pisces
(Detriment)
Mercury in Pisces are psychic, sensitive cry babies. The can be shy and lacking in self confidence. They are prone to the addictions, they have a hard time with the truth and feel everybody is mean to them, they tend to follow their illusions. Mercury in Pisces is in its Detriment, the energy of the planet and sign do not work well together causing a conflict.