Got my voucher... now how to leverage?

I used to play around with Adwords a few years ago, but never made a profit. I would promote my website with clickbank products, and I even tried promoting the hoplink itself (silly me). My account's still good and working.

Now I'm staring at "$100 in free advertising", so why shouldn't I leverage it? Problem is, I've never turned a profit on Adwords.

So what do you guys do with Adwords?