Recommendations from people you know will always be the strongest motivator for purchasing, and will always be more valuable than any other form of marketing or PR. Referrals aren't just limited to friends, family and colleagues, it can come from any source the customer trusts. This might include news publications, customer reviews, testimonials or influencer opinions (bloggers, for example).
Why? If you hear a positive opinion about a product, brand or service from somebody you know or trust, you automatically trust the brand/organisation significantly more and will be more convinced to purchase. Brand trust is something companies spend thousands of pounds trying to achieve, but by encouraging referrals you can authentically achieve this much better than any other way.
There are many ways of encouraging referrals. I've listed my favourite 7 below:
 Create a referral campaign. Reward customers for sharing your brand by providing them with an incentive. You can also reward the receiver if they make a purchase on the back of the referral. Dropbox's famous referral programme gives you and your friends 500MB additional free storage space, up to 16GB, when you refer. Uber did something similar, giving you and a friend money off a ride when you refer. Importantly, what you give to the referring customer has to feel as food as to the new customer. There are some great programmes out there to help you set up your referral campaign... Some of them include: Woobox, MentionMe, Ambassador, ReferralCandy, Friendbuy, LoyaltyLion, & Referrify.
Note: A referral campaign doesn't have to be online. Last Christmas I gave all my customers who purchased in November or December a voucher to either use for themselves, or to give to a friend for Christmas. The receiver of the voucher would never know it was a freebie!
 Create sharable content. Encourage individuals to share content on their social platform, and you can reach potential customers who not only now know about your brand, but have found out about it through somebody they know.
 Implement exceptional customer service. Encourage customers to go away shouting and screaming about how amazing their experience was.
 Encourage influencers to talk about your brand. These influencers need to have a readership as close to your target market as possible, and you can reward them with a free product, or a % of sales. There are a few great programmes out there depending on the size of your company and campaign, which automate referral campaigns like this. I used to use one called LeadDyno, which integrated well with my Shopify store, and was extremely cost effective. If you are working with a really high profile blogger, they may ask for a one-off fee instead or as well as their commission. If you can't afford the larger influencers, there are plenty of other bloggers out there with smaller influencers who may be willing to do it for a minimal fee, or no fee at all. These influencers are just as important as the big ones.
 Make it easy to refer. For example, have a link visible on your website or email campaigns, where in one click the customer can share content (via social, via email etc). Don't make it possible just for those who purchase, have it available to as many visitors of your company as possible. You can have it visible on a home page, account page, a separate landing page or in your emails, for example.
 Encourage Reviews. People trust what other customers say about a company, so make sure you encourage reviews. Do this by making it easy for them to leave their review after they have purchased.
 Surprise your customer. A great way to do this is by sending gifts either randomly or event specific (e.g. Christmas). By giving to a customer you will encourage them to give back, and one way they may do this is by recommending you. You could even do this by sending them a note a few months after purchase just checking up on them that they are happy with their product/service, and offering them any tips or help.
It's worth noting that although I have focussed on referrals in this post, a lot of the above ideas are also relevant to increase retention. I'll focus on a retention post soon. :)