But a set of highly contested unwritten rules has also evolved over time -- rules players pay just as much attention to.
One is "Don't mess with my mound" -- at least, if you are Dallas Braden. In 2010, New York Yankees third baseman Alex Rodriguez ran from first to third on a Robinson Cano foul ball. On his way back to first, he crossed the pitcher's mound, and Braden, with the Oakland A's, took offense and yelled at Rodriguez after the inning ended. Rodriguez was unaware he had done anything wrong.
"That was the only time honestly I've ever even seen that," D-backs reliever Brad Ziegler said. "It was something I never would have even thought of until it happened. I don't know if I would have had the same reaction Dallas did, but his passion for certain things is a little different than mine."
There are some unwritten rules that seem to be mutually agreed upon, like don't flip the bat or take too much time circling the bases after a home run.
"To me personally, that's not necessary," Ziegler said. "I don't like it, but that's not just me being a pitcher, that's me being a baseball purist. I don't like anything that draws attention to an individual."
One individual who has taken his sweet time around the basepaths after an extended swing and bat flip is Boston Red Sox designated hitter David Ortiz. According to D-backs pitcher Bronson Arroyo, it became more acceptable in his situation because of how he carried himself.
"It seems like it's easier to deal with when guys have some kind of seniority in the game and have produced for a long time," Arroyo said. "It almost seems like it depends on the personality."
Demeanor is all that matters to Padres first baseman Yonder Alonso. He's an enforcer of unwritten rules, familiar with most of them and unhappy when he sees them broken.
"I'm kind of an old-school guy, so I respect those things and I'm always looking out for those things," Alonso said. "I think everybody knows those rules, even though they're not set and I know for me, I take it personal."
Padres shortstop Clint Barmes learned a lesson at the top of Alonso's list the hard way. It's what Barmes called the "Up five after five" rule, an unofficial decree that says no bunting or stealing if a team is up at least five runs after the fifth inning. He broke it early in his career before he was aware of it.
The result: An earful from the opposing team, as well as his fellow Rockies teammates who made sure he never led off with a bunt again in that situation.
"I was younger -- that was part of the learning experience for me," Barmes said. "In that situation where we were at, it was not the right move, not the right play. Looking back at it, it's something that is definitely frowned about by the opposing team."
But different players have different takes, which is why unwritten rules have been and will continue to be controversial.
For Arroyo, Barmes' situation makes his head spin.
"You shouldn't be able to tell other people what to do inside of the game," Arroyo said. "We're competing. I'll do what I want to do and you do what you want to do, and we'll see how it shakes out."
Nick Krueger is a junior majoring in journalism at Arizona State University. This story is part of a Cactus League partnership between MLB.com and ASU's Walter Cronkite School of Journalism and Mass Communication. This story was not subject to the approval of Major League Baseball or its clubs.