According to Niccolò di Bernardo dei Machiavelli
  1. If possible, inherit a monarchy from a parent or relative. These are the easiest people to rule because everyone is used to your family dynasty.
  2. If you can't inherit a monarchy, look for an existing monarchy to conquer. If you can't find one of those, look for a republic to conquer.
  3. Look for a monarchy/republic that speaks the same language as you do. The transition to your rulership will be easier this way.
  4. Try for a monarchy where you don't have to share power with barons or ministers who could at some point turn on you.
  5. If you have to try for a republic, you'll have to utterly destroy it first before the people will accept government without representation. Be merciless. Burn everything to the ground. Take no prisoners.
  6. It will be easier to crush the nation you want to take over if you already have your own, long-standing royal army than if you have to hire mercenaries.
  7. Kill anyone who doesn't like you or talks shit about you.
  8. Be horrible and often seem irrational.
  9. As people accept your rule, you can become less cruel. This way, the people won't hate you or want to overthrow you.
  10. Always be wary of nobles who might plot against you. Kill them first before they kill you.
  11. Make sure the capital is well-garrisoned and always vigilant and prepared for imminent attack.
  12. If possible, appoint yourself as head of the church of the predominant religion.
  13. Pay your army well. They are better than expensive, lazy mercenaries and auxiliary forces who also serve their own interests.
  14. Wage war against other countries 365 days a year. This will distract the people and give them something to root for.
  15. Don't be nice or polite. Be honest about your thoughts, feelings and intentions.
  16. Don't be "generous" with your people because you will have to tax them to afford it. People would rather you be greedy and stingy because it means lower taxes.
  17. Unless you can conquer another nation and take all of their stuff. It is okay to be generous with the spoils of war with your people.
  18. Don't be very compassionate, as a rule, but occasionally show mercy to someone so the people don't hate you.
  19. Lie to everyone. But don't get caught in your lies. Have scapegoats at hand, just in case you need to pin something on them.
  20. People will not all-the-way hate you if you leave their family and property alone. This will keep you safe from internal threats/rebellion, probably.
  21. When you conquer other countries, try to get them to become friends with each other so they don't conspire against you.
  22. Sometimes it is good to stir up trouble in one of your conquered countries as a distraction during hard times.
  23. Build large, impenetrable fortresses in which to live and hide and keep yourself safe.
  24. To win respect, win wars.
  25. If neighboring countries are quarreling, take sides. But choose the winning side. This will make you appear smart and strong.
  26. Throw parties, declare holidays, give out meaningless awards and occasionally show up on the battlefield and give a speech on horseback, wearing an attractive, velvet mantle. This will help make people hate you less.
  27. Choose only the very smartest ministers and advisors.
  28. There is no such thing as luck. If you want to be emperor, no one is going to hand it to you. You have to take it for yourself.
  29. When in doubt, be impulsive.