One often-missed opportunity: Stacking to earn rewards across several programs and sites. Let's say you're booking a hotel for your next vacation. There's the hotel program, obviously, and points or cash for using a particular credit card. But shoppers could also start their purchase at a rewards portal like Ebates.com, which offers 1.25 percent cash back on purchases made at booking site Orbitz. Then Orbitz itself awards 3 percent back in site rewards on hotel purchases. (Some hotels will only offer rewards on rooms booked directly; it's up to the traveler to decide whether it's better to get an extra discount through a booking site or accrue points toward a free room.)
To put a value on that, a $1,000 hotel booking would generate $12.50 cash back at the portal, $30 in rewards for a future Orbitz.com purchase and $20 back on a credit card with 2 percent cash-back (like Citi's Double Cash).
Grocery shoppers could earn points in a manufacturer's program (like Kellogg's or Huggies) as well as points toward deals in a supermarket program. In stores including Safeway, Stop & Shop and Giant Eagle, users typically rack up points to get discounts at participating gas stations, said Teri Gault, founder of TheGroceryGame.com. There can also be seasonal deals like discount amusement park tickets, bonus gift cards or a free Thanksgiving turkey for shoppers who hit specific spending thresholds. The grocery purchase could earn credit card rewards, as will any subsequent gas purchases.
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If a few extra points or cash-back aren't enough of an incentive, consider that portals and credit cards often attach extra discounts or bonuses to the transaction, Bodge said. United's Mileage Plus Shopping Portal is offering 500 to 2,500 bonus miles to shoppers who link to their favorite retailers and spend $150 to $700 before Monday. FatWallet.com awards 2 percent cash back on Gap purchases, and still lets shoppers use digital coupons like a recent one worth 30 percent off full-price styles.
Shoppers who want to condense their rewards for a quicker payout aren't without options, either. When the goal is a free airline ticket, for example, a shopper could start at that airline's shopping portal and use a credit card that earns miles in the program or allows for reward transfers. Chase and American Express allow point transfers to partner travel providers; so does the Starwood Preferred Guest hotel program.
Update: This story has been updated to reflect hotel program limits on rewards earned.