Who's this guy whose blog you're reading?

Here's another homonym pair that mixes up many a writer, even professionals. Proper use of who's and whose is a little tricky, but like the rest of the rules of English it's not that difficult to get it right with a little thought.

(You can see an example of MSNBC getting it wrong -- it should be whose life, rather than "City Worker Meets Family Of Man Who's Life He Helped Save")

Who's is the contraction of who and is. Whose is possessive. If you want to get it right, just sound it out fully before you put pen to paper (or fingers to keys) -- if you mean "who is that guy" or "who is going to write that," then use who's. Otherwise, whose is probably the word you are looking for.