One of the most popular approaches to travel hacking is finding deals that "stack:" when you can apply multiple techniques to a single transaction, you can bring your out of pocket expenses even lower than you would applying any one of them individually.
Some deals stack
Since stacking deals can amplify total savings, deals that stack tend to get a lot of attention. For a simple example, you might click through a cash back portal to Hotels.com, apply a Hotels.com coupon, and pay for your stay with an Arrival Plus card. The cash back portal and coupon lower the amount you're charged, and then your final out-of-pocket cost is reduced further by redeeming against the transaction Arrival Plus miles you've manufactured as cheaply as possible.
Stacked deals can get much, much more complicated that that: Frequent Miler has painstakingly shown how portal cashback, coupons, credit cards, and even the tax code can be stacked to earn a Southwest Companion Pass with as little out-of-pocket expense as possible.
Most deals don't stack
What's usually glossed over by credit card salesmen is that most deals don't stack, which is important to both understand and take into account when developing a travel hacking strategy.
To take an example from last Thursday's post, the 4th-night-free benefit of the Citi Prestige card gives a roughly 25% discount off paid stays of exactly 4 nights. Ideally, you'd like to stack that with something like the Barclaycard Arrival Plus or BankAmericard Travel Rewards credit card, to redeem cheap points against your final bill. But because the stay has to be paid for with the Citi Prestige, your discount is limited to 25% — less than you'd save simply paying for a 4-night stay with one of those credit cards.
Another example is the American Express Delta Platinum and Reserve credit cards, which offer an annual companion ticket in economy (Platinum) or first class (Reserve). Such tickets offer a discount of almost 50% off 2 domestic tickets (though only the primary ticket earns redeemable and Medallion Qualifying miles). But manufacturing spend at grocery stores with a US Bank Flexperks Travel Rewards card offers a discount of, for example, between 53.2% and 68.9% on paid airfare! Buy two tickets with Flexpoints and not only are you unconstrained by fare class, but both tickets will earn miles and be upgrade-eligible, as well.
That doesn't mean the Delta American Express cards are bad cards (I personally have a Delta Platinum small business card). It does mean you need to think critically about the value of the companion ticket, perhaps using it to book travel for friends or relatives who will reimburse you (maybe) rather than using it for your own travel.
The question, "can I stack this deal?" should be one of the first ones you ask whenever you see a pitch for a new credit card or discount on purchased points, but also as you proceed through your everyday routine. If the answer is yes, you can amplify your savings by applying as many angles as possible to each transaction.
If the answer is no, that doesn't render a deal instantly worthless. But it is an invitation to examine the deal more closely, to ask whether and how you'll incorporate it into your overall travel hacking strategy. It may turn out to be superior to your other techniques, and it's those other strategies that should yield to the new, cheaper method of paying for your travel.
But if it offers a smaller discount (like the Prestige 4th-night-free), less-flexible booking options (like the Delta companion tickets), or interferes with your other goals, like elite status requalification, then you should take seriously the possibility that you will get less value, or have greater out-of-pocket expense, then you would pursuing a different strategy that incorporates more, better, and stackable deals.