Quite frequently now I am seeing hotels, large and small, offering discounts "mention Twitter code #abc123". I've recently tweeted "anyone recommend a Boston area hotel/inn under $200?" and several area lodging establishments tweeted me directly with offers and discount codes not available on their websites. This enables the establishment to know exactly where their business is coming from. You can't ask for a more convenient and free method of advertising providing the capability of tracking your ROI. If you don't want to publicly offer discount rates on your website, this is a way to be selective when you see the demand pop up on your Twitter stream. Set up a column for relevant key phrases pertaining to your business and location and watch that stream for that opportunity. From Hootsuite (or your preferred Twitter client) post it to Twitter and Facebook. But I'd create one for Twitter and one for Facebook, enabling you track the ROI from each, separately.