1) Buy experiences, not things: This is a well-documented principle. Adventures make stronger and longer impressions on our brains than new boots do. Or as the authors eloquently put it, "After devoting days to selecting the perfect hardwood floor to install in a new condo, homebuyers find their once beloved Brazilian cherry floors quickly become nothing more than the unnoticed ground beneath their feet. In contrast, their memory of seeing a baby cheetah at dawn on an African safari continues to provide delight."
2) Help others, not yourself: Because humans are so profoundly social, studies show that people across cultures are happier when they spend money on other people, rather than themselves. So go ahead and buy that expensive scarf, but give it to your sister.
3) Buy lots of little things, rather than one big thing: People adapt to having new stuff, and anything that disrupts that adaptation is likely to prolong happiness. Just as you start to get used to that one new blouse, up comes another one. As the authors explain: "Having a beer after work with friends, for example, is never exactly the same as it was before; this week the bar had a new India Pale Ale from Oregon on tap, and Sam brought along his new friend Kate who told a funny story about dachshunds. If we buy an expensive dining room table, on the other hand, it's pretty much the same table today as it was last week. Because frequent small pleasures are different each time they occur, they forestall adaptation."
4) Don't buy the warranty: Remember that time you cracked your iPhone, and you thought you'd go back to the Apple store for a replacement right away, but instead you just kind of used the cracked one for another four months until the new version came out? And it was pretty much fine? People adapt to good things, the psychologists write, but they adapt to bad things, too. The "psychological immune system" will find a way to spin the iPhone accident positively. (At least the cracked one is less likely to get stolen, our internal Pollyanna might say.)
5) Buy now, consume later: Not only does this principle help build anticipation—another happiness driver—it also foments uncertainty about the reward and helps us make better, more future-oriented choices. It's a good thing Christmas, with its presents sitting under the tree for days, has a built-in delayed gratification mechanism.
6) Consider the details: Much of our happiness is determined not by big life changes, but by the annoying little hassles (or tiny "uplifts") that pepper our days. "Consider the choice between a small, well-kept cottage and a larger 'fixer upper' that have similar prices," the authors write. "The bigger home may seem like a better deal, but if the fixer upper requires trading Saturday afternoons with friends for Saturday afternoons with plumbers, it may not be such a good deal after all."