From youtu.be/FN4eDk1pq6U: Word of mouth is much more credible and targeted (relevance + timing) than targeted advertising.
Timelessness - Focus on psychology, not technology. The platform will change (Instagram, Twitter, Facebook, MySpace, etc.), but the audience won't.
Crafting - Spend your time crafting a great message, not finding a great messenger. A great joke-teller can make dumb joke funny (to their audience). A great joke is funny no matter who's telling it (a much wider audience).
Homophily - If you like something, you probably know others who will like it as well. When someone buys something from you, give them another for free -- "If you like [this], please consider sharing the included extra with a friend."
Monkey see, monkey do - Apple originally had the laptop logo facing the user, (if closed), as a guide for easy opening. They eventually flipped it to display upright for onlookers, so they could identify the Apple, and think about the brand.
Reverse Psychology - When you tell someone NOT to tell a secret, they'll tell everyone. How Please Don't Tell violates the most fundamental rules of marketing, but is better off for it.
Top of mind, tip of tongue - Rebecca Black's "Friday" is mostly shared on Friday. Peanut butter and ..... (you think of jelly -- "peanut butter" is like a mini-advert for jelly). Link your product with something else (a set of queues / triggers that grow your product). Kit-Kat linked to coffee "Have a coffee, Have a Kit-Kat." Why? People drink coffee many times per day, making them think about Kit-Kats frequently -- "Leap Day" song would not have been as successful as "Friday"
Action - Positive vs. Negative, High vs Low Arousal, emotions chart. Ex. Anger, (negative/high), is activating. Sadness, (negative/low), is deactivating. Low arousal decreases sharing. "Running" in a commercial, even if irrelevant, increases arousal, and sharing.