You can find a list of current promotions at TVG.com/promos. On the desktop site you can navigate there by hovering your cursor over Promotions and clicking on Live Promotions.
From a mobile device you can view all available promotions by tapping Promos in the blue navigation bar.
Above each promotion you will see a tag listing if it is a promo or a contest. If you have already opted in to a promotion you will see a tag that reads "opted-in" in its place. Contests do not require that you opt in but you will need to opt in to any promotions you would like to participate in.