You should not place a colon between a verb and its object or subject complement, or between a preposition and its object. Here are some situations in which an incorrect use of the colon is presented, followed by an explanation and some ways of correcting the incorrect example.

[INCORRECT] His neighbour lent him: a pup-tent, a wooden canoe, and a slightly battered Coleman stove. 

This shows an incorrect use of the colon because the colon appears between the verb and its objects. The colon must be preceded by an independent clause. Here are two ways in which the above sentence may be corrected. Notice how one uses commas, while the other uses a colon:

• His neighbour lent him a pup-tent, a wooden canoe, and a slightly battered Coleman stove.

• His neighbour lent him a few camping supplies: a pup-tent, a wooden canoe, and a slightly battered Coleman stove.

[INCORRECT] Her three goals are: to improve her public speaking skills, to increase her self-confidence and to sharpen her sales techniques. 

This shows an incorrect use of the colon because the colon appears between the verb and the subject complements. Here are two ways in which the above sentence may be corrected. Notice how one uses commas, while the other uses a colon:

• Her three goals are to improve her public speaking skills, to increase her self-confidence and to sharpen her sales techniques.

• Her three goals are as follows: to improve her public speaking skills, to increase her self-confidence, and to sharpen her sales techniques.

[INCORRECT] We travelled to: London, Wales and Scotland. 

This shows an incorrect use of the colon because the colon appears between the preposition and the objects of preposition. Here are two ways in which the above sentence may be corrected. Notice how one uses commas, while the other uses a colon:

• We travelled to London, Wales, and Scotland.

• We travelled to three countries: London, Wales, and Scotland.