Colons serve two primary purposes. The first is to precede a list of three or more things in a sentence, and the second is to join two clauses, where the first clause is an independent, and the second clause is a dependent clause that explains the main clause. If being used to connect two clauses, the first clause must always be a independent clause.

The sentence above is correct as written. 

Colons serve two main purposes. The first is to precede a list of three or more things in a sentence, and the second is to join two clauses of a sentence. For the first purpose, however, you should avoid using a colon after a verb or a preposition. The best way to correct the sentence above is to delete the colon. 

Colons serve primarily two purposes. The first is to precede a list of three or more things in a sentence, and the second is to join two clauses of a sentence. For the first purpose, however, you should avoid using a colon after a verb or a preposition. The best way to correct the sentence above is to delete the first colon; the second one is correct and necessary, but the first is both redundant, and directly follows a verb.

Colons serve two main purposes. The first is to precede a list of three or more things in a sentence, and the second is to join two clauses of a sentence. For the second purpose, however, you may only use a colon where a period might otherwise be used. Because the first clause in the sentence above could easily stand on its own, and could terminate in a period, the use of the colon above is correct and proper. The sentence contains no error and is correct as it is written. 

Be watchful of possessive plural nouns: here, the correct apostrophe will be at the end of the word: "boys'" is correct because the subject is plural.

The correct possessive form for "children" is "children's," not "childrens." "Children" is a noun that changes form in plural, from "child" to "children" instead of "childs." In irregular plural nouns that do not end in "s," you need to add an apostrophe followed by an "s" to form the possessive form of the word. For plural nouns ending in "s" such as "girls," you need to add the apostrophe at the end, but not an "s." For example, the possessive of "girls" is "girls'."

The above sentence's error is "the Davis's," as "Davis" is not a possessive noun in this case and therefore does not need an apostrophe.

The sentence indicates that there is more than one girl on the team by using the word "they;" therefore, "the girl's" needs to be changed to "the girls'" in order to reflect the correct possessive plural form.  

The correct possessive form for "children" is always "children's" and never "childrens'."

The plural of goose is “geese,” not “geeses,” so the correct possessive form would be “geese’s.” "The better part of" is a commonly used phrase, and "have been tracking" and "have begun" are both the correct forms of the present perfect.