This bed bug infestation video really shows how you can not really know that you have bed bugs until you are infested.
Recommended Products To Protect Against Bed bugs:
Mattress Encasements - goo.gl/7jBCdC
BedLam Bedbug Spray - goo.gl/RXHRn9
Essentria IC3 - goo.gl/hTREN5