Punctuation is one aspect of English where you can learn the rules, and they will almost always remain consistent. Here are some resources to guide you.

General Overview

The Writing Centre at Royal Roads has put out a good primer on Punctuation.

The University of Toronto also has its own Punctuation page, and a Hit Parade of Errors featuring common issues punctuation, grammar and style.

Specific Punctuation

An extremely important skill to develop for writing essays is the proper use of quotation marks. Here is Purdue’s OWL page on them. Also see their Extended Rules for Using Quotations, and their Additional Punctuation Rules pages.

The University of Minnesota has a page on Quotation Marks that details the differences between single and double marks.

The University of Wisconsin describes Using Semicolons on this page.

Check out The Oatmeal’s excellent illustrated guide How to Use  a Semicolon.

Grammar Girl’s Quick & Dirty Tips offers a good guide on how to use Colons.

Grammarbook.com also provides a detailed page on Colons. It also gives good advice on how to use Apostrophes.

Once again The Oatmeal uses humor and drawings to explain How to Use an Apostrophe.

One common mistake students make is the Comma Splice – joining two complete sentences together with a comma, rather than a period of joining word.