Acolon must follow
an introductory phrase
a subordinate clause
an independent clause
a long quotation

A colon must follow an independent clause. It can equally follow a lead-in sentence and the sentence which precedes the colon must make grammatical sense on its' own. It can also precede a phrase, a clause, a series or a lengthy quotation. Often the first part of the colon should amplify the second part of the colon or that the second part of the clause is a result of the first.

Amman jordan is da capital