1. Reciprocity

The principle of reciprocity means that when someone gives us something we feel compelled to give something back in return. Have you ever gone to Costco ended up with an unplanned sausage purchase in your cart because you felt a nagging obligation to buy because you tried a free sample? Well, that was the principle of reciprocity in action.

Of course, online retailers can’t personally visit the house of each person who interacts with them to shove a sample in their hand. So how can you make reciprocity work for you?

2. Commitment & Consistency

The principle of commitment and consistency says that people will go to great lengths to appear consistent in their words and actions – even to the extent of doing things that are basically irrational.

That’s why if you’re trying to make a change in your life – losing weight, for example – it can be very helpful to state your goal publicly. Once you’ve committed out loud (or online) you will have much more incentive to keep up your end of the bargain.

As a retailer, if you can get customers to make a small commitment to your brand (like signing up for your email newsletter), they are more likely to eventually purchase from you. And if you can actually get products in their hand, even if there is no official commitment to buy them, your chances increase even more.

3. Liking

The principle of liking says that we are more likely to say yes to a request if we feel a connection to the person making it. That’s why the sausage sample lady at Costco is always giving you a nice smile.

It’s also why brands hire celebrities to endorse their products – so that people will transfer their love of Roger Federer to watches he’s endorsing.

There are lots of ways to make this principle work for your store:

Telling Your Story

As a direct-response marketer I tend not to truck much with branding. But if there’s one place that branding is essential, it is in triggering the principle of liking.

Every element of your store – colors, fonts, photo styles, copy – contributes to your brand personality, and your goal is to create a personality that is cohesive and that your target customer will like. This might be brisk and efficient if you are selling into a business market, warm and playful if you’re selling children’s products, ‘earth-mothery’ if you’re selling natural products.

Use Models People Can Identify With

If you’re selling clothing, jewelry, or accessories, one quick way to create a connection to your customer is to show your stuff on people they will identify with and like. This doesn’t mean you need to book Russian supermodels; it’s best if they look like your customers.

Social Links

People are more likely to purchase something if it’s recommended to them by someone they know and trust. So make sure that your product pages have links to Twitter, Facebook, Pinterest, and Google+ so that your customers can tell their friends about the great product they just found on your site.

4. Authority

Most people have heard of the famous Milgram experiments, in which volunteers were convinced to continue delivering what they thought were incredibly painful electric shocks to unseen subjects, even when they could hear (faked) screams of pain. The presence of a man in a lab coat telling them to continue was enough to earn the compliance of nearly all the volunteers.

People appear hard-wired to respond to authority (or the appearance of authority). How can you use this to sell?

5. Social Proof

The principle of social proof is connected to the principle of liking: because we are social creatures, we tend to like things just because other people do as well, whether we know them or not. Anything that shows the popularity of your site and your products can trigger a response.

Have you gotten good press? Mention it! Received loving emails from customers? Quote them! Gotten good feedback from your mom? Heck, get it up there.

6. Scarcity

Cialdini’s final principle is the principle of scarcity, which states that people are highly motivated by the thought that they might lose out on something. Call it the Eternal Teenager Principle: if someone tells you that you can’t have it – boy, do you want it. This is probably the one I’m the biggest sucker for, personally.

Marketers trigger this effect by using all kinds of tactics to suggest that products (or low prices) might soon be gone, or that someone is trying to keep this product off the market.

Seasonal or Limited Products

Every March when my friend gets her green Shamrock Shake from McDonalds she crows with happiness all over the social media. Think she’d be that excited if she could walk in and get it any time? Of course not. The knowledge that the supply is limited motivates her—and makes her feel like a success for having “won.”

But What About Pricing?

You may be wondering where the extremely common retail tactics of sales & discounts fall under these six principles. Is Cialdini saying that price doesn’t impact people’s purchasing behavior?

Of course it does, and Cialdini mentions a couple of pricing experiments in the beginning of his book. But think of it this way: the price of your product represents the size of a risk someone is going to take on. In other words, people will be a lot more choosy over a $10,000 product than one that is $1.

Risk Removal

The six principles of influence represent additional non-obvious ways to impact perceived risk. For example, by using appeals to authority, you’re decreasing the risk of a ‘yes’ – someone who says yes (to your appeal to buy a product) can always point to the authority you’ve demonstrated to rationalize their purchase. By using scarcity tactics, you’re increasing the risk of a ‘no’ – someone who declines your offer right now might miss out.

So given a price that you have settled on for your products, using the principles of influence can decrease the risk of ‘yes’ (liking, social proof, authority) or increase the risk of ‘no’ (scarcity, consistency, reciprocity).

Sprinkle them throughout your site and watch your sales go up!