Semicolons and Colons

Semicolons ;

A semicolon looks like a period riding piggyback on a comma.  It can join two independent clauses, performing the same function as a comma and and.

I went to the store, and she went to McDonalds.
I went to the store; she went to McDonalds.

It's less work to use a semicolon, it makes you look sophisticated, and it shows the reader you know your stuff. 

You can have two semicolons in the same sentence, separating three independent clauses.

Mrs. Hicks really likes performing stunts on her bicycle;  Evel Knievel preferred a Harley for his stunts; Mr. Ogle typically uses a tricycle.

One comma rule is to separate items in a series, but what if another comma rule requires one or more of the items to have additional commas? 
You guessed it...a semicolon separates the items.

A polar bear likes to chase artic explorers; white, furry seals; and door-to-door salesman.

Colons :

A colon can also separate independent clauses, but when it's used, it's because the second independent clause gives an example or explains the first.

I have one goal left in my life:  I want to ride a bike like Mrs. Hicks does.

A colon can also precede a list of items.

Terry loved several sports: basketball, baseball, and cat juggling.

It would be incorrect, however, to put a colon immediately after a verb and in front of a list.

Incorrect:  Terry likes: basketball, baseball, and cat juggling.

Colons are used to make appositives and appositive phrase stand out moreso than a comma.

I have a favorite dish when I am in Canada: moose burgers.

A colon can precede a long quote as well.

When I see colons in times (3:10 p.m.), separating books from chapter in the Bible (John 3:16), and separating a magazine's volume number from
its number or volume and page number (Time 24) 301:, I don't even think of them as colons, but they are.

A colon is also typically used after the salutation of a formal letter (whereas a comma is used for informal ones).
Dear Mr. Forbes:

Keyboarding note: Old school typists still put two spaces after periods and one space after commas.  Consequently, when they space after
semicolons and colons, they look at bottom of the punctuation and space accordingly:  two spaces for colons and one for semicolons.  Two spaces does make papers look

For MLA papers, consult the latest version of their expensive book.  They change the guidelines every two or three years so they can sell more books,
but the last time I looked, either was acceptable in the body of the paper.  The Works Cited page was different, but you will need to look that up.