While there isn't a list of skills that are universally agreed upon, it's, of course, a good idea to know Astrology and be able to interpret birth charts. Other than that, it may be a good idea to get some experience in social work and counseling. Many clients who approach astrologers are looking for insight into some of the difficulties in their lives, so they aren't just looking to be told what's causing it, but effective strategies on how to handle it.
There are also several astrological diploma courses offered by various groups with the intent to train people into becoming professional astrologers.
There is no minimum or maximum amount of college required to be an astrologer since the field is to the large part unregulated.
Super Astrologer
About the same as a politician. ie none to speak of. The ability to say things that would match a great many people. A smattering of astronomy would be good but not essential. Never be specific about anything and generalise as much as possible.
Walter Koch - astrologer - was born in 1895.
Julia Parker - astrologer - was born in 1932.
John Harvey - astrologer - died in 1592.
John Harvey - astrologer - was born in 1564.
John Partridge - astrologer - was born in 1644.
Jim Lewis - astrologer - was born in 1941.
Jim Lewis - astrologer - died in 1995.
Walter Koch - astrologer - died in 1970.
poosamuthu was the very famous astrologer at vaitheeswaran koil