I recently read it, and I tried to record the biggest and most applicable lessons presented by ol' Niccolo. These are simple distillations, though, so I'd highly recommend reading it for yourself. There's some talk about the Dark Triad on this sub, so here's one of the more learn-able legs of the stool, so to speak.

Note: page citations are from the edition found here: http://www.constitution.org/mac/prince.pdf

Let's get into it:

  1. Either treat a person well or crush them entirely – do not leave any ability to seek revenge if ever you should give them cause for it.

  2. Wise men foresee trouble before it occurs and are able to easily deal with it – by the time everyone can see it, it becomes a problem without a good solution.

  3. War is never avoided. It is merely put off to the advantage of others.

  4. “The wish to acquire is in truth very natural and common, and men always do so when they can, and for this they will be praised not blamed; but when they cannot do so, yet wish to do so by any means, then there is folly and blame.” (p. 13) The example given here is King Louis XII of France, who wished to acquire more and more territory so badly that he ended up sacrificing his position in other greater territory.

  5. “He who is the cause of another becoming powerful is ruined; because that predominancy has been brought about either by astuteness or else by force, and both are distrusted by him who has been raised to power.” (p. 15)

  6. “A wise man ought always to follow the paths beaten by great men, and to imitate those who have been supreme” (p. 22)

  7. Great men owe nothing to fortune other than mere opportunity, which presents them only with the material that they themselves must mold

  8. “It ought to be remembered that there is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new” (p. 24)

  9. People are easy to persuade but difficult to fix in that persuasion.

  10. To stand only on the goodwill and fortune of any person who has elevated you, and not on your own ability and recognizance of opportunity, is utterly perilous and unstable.

  11. In other words, “he who has not first laid his foundations may be able with great ability to lay them afterwards, but they will be laid with trouble to the architect and danger to the building” (p. 28)

  12. Men injure only from either fear or from hatred – watch out for those with both the power and the cause.

  13. “Injuries ought to be done all at one time, so that, being tasted less, they offend less; benefits ought to be given little by little, so that the flavour of them may last longer” (p. 42)

  14. It is difficult to manage people who consider themselves your equal.

  15. A wise man must adopt such a course so that his friends and the people around him will always in every circumstance have need of him – and not the other way around.

  16. Men will always be adverse to undertake enterprises where difficulties are easily seen – so make your strengths well-known.

  17. “It is the nature of men to be bound by the benefits they confer as much as by those they receive.” (p. 50).

  18. Do not rely too much on the help of others, because even when you win, your victory becomes theirs and not your own anymore.

  19. A wise man must always and industriously be increasing his resources in times of plenty and peace, so that when the winds of fortune shift, he will be more prepared to deal with the blows.

  20. Generous behavior exercised in uncalculated ways will not cause a reputation for generosity, and will even leave you subject to criticism of its opposite – and even as you exercise this generosity, you lose the power to do so.

  21. It is better to be feared than loved – love serves you with promises which are easily broken, but fear serves you with the threat of punishment that is not to be avoided (love is at the will of others, fear is at your own will).

  22. That being said, inspire fear carefully and without inspiring hatred – always act justly.

  23. “You must know there are two ways of contesting, the one by the law, the other by force; the first method is proper to men, the second to beasts; but because the first is frequently not sufficient, it is necessary to have recourse to the second.” (p. 83)

  24. “He who seeks to deceive will always find someone who will allow himself to be deceived” (p. 84)

  25. How you appear is often more important than how you actually are – men judge by the eye rather than the hand, so to speak.

  26. Men who are highly esteemed are not easily conspired against.

  27. “A prince ought, above all things, always to endeavour in every action to gain for himself the reputation of being a great and remarkable man.” (p. 108)

  28. It is always better to strongly take a side than remain neutral, no matter which side you actually choose and which one should emerge the winner.

  29. Never ally yourself with someone stronger than you unless absolutely necessary.

  30. The first impression made of you is formed from the impression of the company you keep.

  31. When you observe a person who always acts more in their own interests than yours, you cannot trust them.

  32. Avoid flattery and false advice by selecting several wise individuals and letting them know that the more freely they speak to you, the more you prefer them – and listen only to these opinions.

  33. “A prince who is not wise himself will never take good advice, unless by chance he has yielded his affairs entirely to one person who happens to be a very prudent man. “ (p. 116)

  34. Make it known that you will only take advice when you ask for it – but always ask often.

  35. Men value the present more than the past, and when the present is good, they enjoy it and seek nothing more.

  36. Fortune shows her power where valour has not prepared to resist her – the prince who relies on fortune is lost when it changes.

  37. A prince must seek to change his own ways when fortunes change and always in correspondence with them.

Bonus: "Ill Mind of Hopsin 5" - TRP in every verse. http://www.youtube.com/watch?v=hRVOOwFNp5U

EDIT: Ugh formatting - I'm a busy guy, OK?