"When you make a reservation, many hotels will ask you to enroll in their loyalty club," Mandelbaum says.
These free clubs generally reward guests with points for each stay. Points can be redeemed for free nights or offers from partnering companies such as car-rental firms.
Since the economy crumbled, "We've seen the longest period of double-point promotions by loyalty clubs," says Tim Winship, publisher of FrequentFlier.com.
McInerney says earning lots of points may take you to a level where you're granted extras like late checkout and free Wi-Fi service.
When you're a loyalty member of any status, you may be granted a room upgrade if you ask for it when you arrive and if any upgrades are available, Stone says.
Because booking through nonhotel sites means you may not receive loyalty points, some of these sites have begun to offer their own loyalty points, Stone says.
Another way to receive free extras at many hotels is to sign up for the credit card offered by the loyalty club. "You just have to have the card, not necessarily use it to pay for your stay," Winship says