Caution and Cunning: Never get caught at your game.

After reading this book in its near-entirety, you've surely caught on to the fact that most of the methods used to make friends are a little unconventional and under-handed. A few of them may even be illegal or damaging to your goals, though that all depends on how careless you are in your implementation of the methods. In other words: Don't get caught.

It may seem like a simple concept, but not getting caught can really be the most difficult part of making new friends for Slytherins! Take advantage of the dark alleys of Hogsmeade, the unused classrooms of Hogwarts, and even the quidditch locker rooms when they’re not in use! Always arrange any meetings in a secure, empty location, and be sure to use any spells you know that can assure your privacy. Muffliato in particular is useful if you are using the extortion method, as new friends can get a little loud if they think you're about to sick your goons on them.

Keeping documentation and evidence of your friendly exploits will help you keep your friends, but only if no one finds them. Always make sure to hide your insurance well and have secondary spells in place in case they are ever found by prying Witches and Wizards.

It should go without saying that you should never attempt any of these methods on those who are not your peers or a Ravenclaw. Older wizards will not find your attempts to bribe, extort, or exploit them clever and will probably know exactly how to deal with you in accordance with the law. With age comes wisdom — you may be more clever than your average Hufflepuff, but never get so arrogant that you think you can out-smart your professor or a Ravenclaw. These techniques are the kind you can grow into, and they can be useful to you post-Hogwarts, but always know your current limitations.

And on a final note, may I just say to all the Slytherins out there:

Isn't friendship a truly wonderful thing?