Mercury is the planet closest to the Sun and has an orbital period of only 88 days.  As such, you will always find these two in fairly close proximity to one another with Mercury no more than one Sign away, 28 degrees to be exact.  It rules both Gemini and Virgo and affects how we think and communicate with one another in all media from spoken words to email.  Whether we are logical, intuitive, pessimistic or optimistic can largely be determined by Mercury's placement.  While a person's Natal 3rd House will indicate a lot about their thought processes, Mercury's Sign placement will also heavily influence communication style and skills.

Aries Decisions will be quick and made with a direct approach.  They'll generally be optimistic, to the point and applied quickly.  Slow or foolish types will not be tolerated.  Details, however, are boring, so someone's assistance should be used to assure completion.  These folks are also the ones who cram all night the day before an exam.  Recreational fighting in the form of debates and arguments are likely.  Impulsiveness is greatly increased if in negative aspect to Mars.

Taurus:  These natives may learn rather slowly, but once they have a grasp on something, it's there to stay.   Flexibility should be developed as well as the ability to entertain fresh ideas to avoid being unduly or inappropriately stubborn.  Nonetheless, these folks have a lot of common sense and can express themselves with considerable charm.  This is enhanced further with aspects to Venus.

Gemini: Since Mercury rules Gemini, it will further strengthen the ability and need to exchange ideas and opinions.  These folks like to talk, and I mean TALK.  They're the ones that will strike up a conversation in the line at the bank or McDonald's.  Their thought process is quick and as expected, mercurial, meaning they also change their mind a lot.  Since they get bored easily, they often don't have all their facts in order unless they have aspects that provide more stability.

Cancer: Mercury in Cancer predisposes folks to an outstanding memory, which tends to make them favor the past over the present or future; they are often serious history buffs.  They also have good imaginations, which enhances their creativity, but their thoughts and opinions will be heavily influenced by their emotions rather than logic.

Leo:  These folks have strong organizational and planning skills, are enthusiastic and optimistic.  They express themselves well, but sometimes they treat others in a condescending manner, which they are usually oblivious to but should try to overcome.  The can "think outside the box" but are often stubborn about changing or modifying their ideas.

Virgo: Mercury also rules Virgo, so it's influence here is particularly strong.  The ability to analyze situations and problems down to the most minute detail is outstanding.  However, these folks can get so hung up on details that they don't comprehend the big picture.  They also tend to worry a lot and like to know exactly what is expected of them.  Changes are often troublesome.  These folks should cultivate the ability to think for themselves so that they don't overreact if "the best laid plans of mice and men" fail.

Libra:  Mercury in Libra will slow down the thought processes somewhat because these folks will be preoccupied with identifying and understanding all sides of an issue.  This can incline them toward indecisiveness as they strive to be fair, not take sides or be controversial.  They are usually very charming, sympathetic and understanding and enjoy taking to friends and family.  They don't particularly like to study but will often look for the path of least resistance.

Scorpio:  This placement will provide a tremendous amount of intuition, Scorpio intensity and an interest in finding every possible aspect of a situation.  Ferreting out hidden details and remembering them all makes these folks great researchers, detectives or any other occupation that requires the ability to synthesize data.  Nonetheless, they tend to be introspective, possibly secretive and in some cases obsessive.

Sagittarius:  A wide interest but perhaps limited attention span characterizes this placement.  These folks pick up ideas very quickly, often giving them the appearance of being much more intelligent than they really are.  They are likely to have a strong flair for languages and often love to travel, if not physically via reading or studying.  They need to develop perseverance and not change their interests too often or they'll be lacking in satisfaction and/or long-term accomplishments.

Capricorn:  Cool and objective assessment of every subject or situation will be the norm, though a tendency toward pessimism is likely.  Planning abilities are strong as well as determination and decisiveness.  Conservative viewpoints, traditional attitudes and strong ambition will also be apparent.  This person means what they say and will not be interested in gossip or trivial matters.

Aquarius Originality and unconventional opinions and ideas are likely.  The mind is quick, but these folks are also likely to be easily victimized by nervous tension or find it hard to relax.  They can be stubborn in maintaining their ideas, which generally evolve in a logical manner.  They are usually very friendly and often do well in charitable or social work.  There is often an interest in the distant past or future as well as unusual hobbies.

Pisces Thoughts will tend to be disorganized with decisions usually reached in an intuitive way.  There is considerable empathy for others, but a practical approach to problems seldom arises.  Worry is quite likely and these folks have a vivid imagination that often makes it worse.  They'll usually take the path of least resistance and can be deceitful, though this is sometimes only to avoid hurting others.  Shyness and a lack of self-confidence are also likely.

When Mercury goes retrograde it bogs down communications of all sorts.  People have a hard time understanding one another, computers crash, traffic signals don't operate properly, mail gets lost, mistakes of all sorts are more common, cars break down, and anything purchased during this time of a mechanical nature will usually not work properly.  If your car is a lemon it was probably either purchased or manufactured during Mercury Retrograde.  Avoid such purchases as much as possible during this time and if you absolutely MUST do so buying that extended warranty is probably a good idea.  If it's an appliance or something that requires installation, make sure it is done properly.  If you're not an expert, pay one to do it for you.  If you buy a computer, new software or any kind of peripheral device such as a printer, read all directions before hooking it up.  Geminis and Virgos are particularly affected since it's their ruling planet.  If they're waiting on a business deal, job interview, home purchase, delivery of something they ordered or just about anything else, it's likely to be delayed until Mercury goes direct.