Here is an interesting article someone wrote about how to know of the first red flags of a bed bug infestation:
http://www.thebedbuginspectors.com/blog/bid/77299/The-First-Red-Flags-in-Bed-Bug-Detection
http://www.thebedbuginspectors.com/blog/bid/77299/The-First-Red-Flags-in-Bed-Bug-Detection