For the strip:
* Use quotation marks: "Peanuts," "Calvin and Hobbes," "Dilbert"
* No need to italicize: "Garfield" is correct, not *Garfield*.
For the character:
* No punctuation: Snoopy, Garfield, Calvin, Dilbert
* Capitalize proper nouns: Snoopy, Garfield, but not "a cat" or "a kid"
Here are some examples:
* I love reading "The Far Side" comics.
* Charlie Brown is the main character in "Peanuts."
* Garfield is a lazy cat.
Important Note: Some comic strips have titles that are also the name of a character (like "Dilbert"). In these cases, use the same rules as above, depending on the context.