Don't Be a Jerk.
This one, Guzzardi admitted, is simple to understand yet not always easy to put into practice. Being a jerk - making fun of others, thinking selfishly, making assumptions before doing the work to learn the ins and outs of something - comes naturally to many of us. We might know we're wrong, and we might feel bad or guilty after the fact, but we still mess up a lot. Instead, we need to take those few extra steps to think about how our actions affect those around us, and to remember that nobody wants to help out a jerk. (So yes, being nice can have payoffs above and beyond feeling better about ourselves.)
Don't Believe the Stereotypes.
We all have our groups of friends who are more or less like us. That's well and good. But that doesn't mean people outside of our comfort zones aren't worth befriending. And it definitely doesn't mean that people outside of our friend groups are defined by the broad stereotypes that we assign to them. In fact, people who seem different than us might just be the best friends we could have, and more than likely they're not anything like your preconceived notions of them. (Which leads to...)
Look for Similarities, Not Differences.
Once you've set aside the stereotypes, it's easy to see how much we all have in common versus where we disagree. And in order to get anything done with a group of people, we've got to focus on common ground. Yes, we can acknowledge our differences, but we shouldn't let them get in the way of working, creating a community, and coexisting with each other.