The classic novel The Adventures of Tom Sawyer by Mark Twain tells of a mischievous young boy growing up in the fictional town of St. Petersburg, Missouri, along the Mississippi River. In chapter 13, due to Tom's boredom with school and inability to attract the favorable attention of Becky Thatcher, Tom decides to run away and "lead a life of crime."

On his way down Meadow Lane towards his new life, Tom meets up with his "soul's sworn comrade" Joe Harper. It turns out that Joe wants to run away as well because his mother had beaten him for drinking some cream. The two boys resolve to stand by each other as brothers until death.

Joe's plan is for them to go off and live the life of a hermit, while Tom's idea is for them to become pirates. The only passage that hints at how Tom persuades Joe to become a pirate is this:

Joe was for being a hermit, and living on crusts in a remote cave, and dying, some time, of cold and want and grief; but after listening to Tom, he conceded that there were some conspicuous advantages about a life of crime, and so he consented to be a pirate.

Although the text does not give details about what these "conspicuous advantages" are that Tom mentions, we can imagine Tom telling him how fun it would be to play pirate, live on an island, travel on a raft, rob people for their sustenance, and be free to do whatever they wanted. They do seem to enjoy themselves for a time, adopting pirate names, speaking pirate lingo, and cooking their food over an open fire in the wild.

This is referring to the start of Chapter XIII where Tom and Joe meet (and later get Huck) and decide to run away because of how badly they are being treated.

We don't exactly get told how Tom convinces Joe.  All were are actually told is this:

after listening to Tom, he conceded that there were some conspicuous advantages about a life of crime, and so he consented to be a pirate.

I think if you look a bit before the quote and a bit farther down you can see what the advantages might have been.  Before the quote, Joe wants to be a hermit and get cold and hungry and die.  That's probably not that much fun.

And then afterwards, you see all the cloak and dagger stuff they're doing?  They have passwords (Blood!) and code names and stuff.  It's perfect guy stuff, right?

So I figure Tom told him that he could go die cold and hungry or he could have fun with passwords and nicknames.