Colons

I was recently writing my Teaching Philosophy statement and I opened up with this gem:
"As a teacher, my goals are: to encourage students to be active learners; to give instruction in new ideas that foster passion; and to create connections between the field of environmental science and the practice of environmental science."

My editor was quick to point out that semicolons are never needed in a list when commas will do the trick. Which got me to thinking about the colon and lists. Grammar girl once again has an amazing page on the issue. Basically, colons are the mark of "expectation or addition". That's because the colon signals that what comes next is directly related to the previous sentence. Which brings us to the golden rule of colons:

only use colons after statements that are complete sentences.

It would be wrong to say, "Grammar Girl's favorite hobbies are: skiing and reading" because "Grammar Girl's favorite hobbies are" is not a complete sentence by itself. (And, really, who would rather ski than stand on one foot?) You can often fix those kind of sentences by adding the words the following after your sentence fragment. For example, it would be fine to say, "Grammar Girl's favorite hobbies are the following: skiing and reading" because you've made the thing before the colon a grammatically complete sentence by adding the words the following.

Thanks again Grammar Girl