One of the favorite parts of my job is to recruit people for my company. From experience I have come to realize that no matter how busy you are, outsourcing recruiting and hiring is very shortsighted for a rapidly growing company (things do change when you are 200 employees plus).
Out of all the functional areas one is most likely to spend a lot of time hiring is sales people. Heck, I would say majority of the recruiting time is spent on hiring sales people, since you need lots of them. For developers, marketing, ops, finance, etc. there are tons of tests and other methodologies to figure if someone is any good.
But unless you have hired hundreds of sales people, you may not be as good distinguishing between someone who is really good sales person and one who is really good BSer.
What I have seen is companies requiring your past W2s. It is fine and dandy if you want to volunteer that info, but the practice of requiring W2 is really something I am against.
So the question I have: instead of asking for W2 to figure out their past performance, what do you do to figure out who is a really good sales person and who is just a great BSer?