about • around
- Few people can afford to go on a cruise (a)round the world. (Not *about*)
((a)round for circular movement)
- They've built a motorway (a)round London.
(= surrounding, encircling)
- The fax was received at around/about 8 pm.
(= approximately; but approximately in place of around and about is very formal)
- The journey took about/around an hour.
(Not *an hour about* *an hour around*) (preposition + object)

about • on • over
- Have you read this article on the Antarctic?
- There's an article about tourism in today's paper. (preferable to on)
(on for serious and specific information; about for general interest)
- Let's agree to differ. Let's not have an argument over/about it. (Not *on*)
(over after argument, concern, dispute)
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