Go here for more info about HBO and for a live channel guide to tell you what's on! A good idea is to record as many movies as you can onto your DVR (if you have one) and then watch them over time when the preview is over.
We're especially excited about The Adjustment Bureau, which apparently premiered on HBO this week!
DirecTV customers check out channels 501-511 for HBO and try pressing channel up from 511 for Cinemax
Dish customers try 300-314 for HBO and Cinemax
(Thanks for the heads up on this free preview, Hip2Save!)