Being knighted today holds a much different meaning than it did in the days of old. Nations with a monarch as their head of state would, once upon a time, issue knighthoods to their loyal subjects and foreign citizens who have done great deeds for their country. Today, you can earn a knighthood through military badassery or if your artistic, scientific, or civil service shines greatly upon the crown. No squiring or learning to fight on horseback required! Then again, you could also be a genocidal Marxist dictator who overthrows the government and you'll eventually be knighted — or you could just be a penguin.
While various knighthoods exist, we'll be discussing the two most recognized: The United Kingdoms' Order of the British Empire and the Holy See's Order of St. Gregory the Great. Fun fact: Bob Hope earned both of these.
Here are the ways you can earn modern-day knighthood
Order of St. Gregory the Great
To be knighted by the Pope into the Order of St. Gregory the Great, you must do something good for the Holy See by setting an excellent example for their community and country. Though usually reserved for Catholics, there have been exceptions made for converts and non-Catholics.
A notable knight is Wilfred Von der Ahe, co-founder of the Southern California supermarket chain, Vons. He and his wife were well-known philanthropists in Los Angeles and would donate much of their earnings to Catholic churches in the area. Von der Ahe was a founding donor to the Cathedral of Our Lady of the Angeles after the previous mother church of the Archdiocese of Los Angeles was severely damaged in an earthquake.
So, in short, help out a church and you could become a knight.
Order of the British Empire
Formal knighthood is definitely the easiest. The Queen remains fairly neutral in political matters, so she chooses to not elect her own knights and appoints everyone chosen by the Cabinet Office twice a year. The only real stipulation is you have to be recommended for doing something good for the Commonwealth of Nations. Though highly illegal, because you need to be nominated by British politicians, people in the past have been nominated to knighthood through political donations.
You don't need to go that far, though. It seems like every British general officer, professor, and celebrity is knighted eventually. Since you don't nominate yourself, there have been a few instances where people have turned down the honor. David Bowie, for example, was offered the Commander of the Order of the British Empire in 2000 but politely declined. He was offered full knighthood in 2003 and again declined. He said, "I would never have any intention of accepting anything like that. I seriously don't know what it's for. It's not what I spent my life working for."
Anyone can get this award, but only Brits get the title of 'Sir' or 'Dame' before their first name.