Just 20 lawmakers have argued for a president's impeachment on the Senate floor -- seven during the trial of President Andrew Johnson in 1868 and 13 during for the trial of President Bill Clinton in 1999.
"I don't recall working any more intensely when I was a congressman to get it right," former Rep. Bill McCollum, R-Fla., told ABC News.
Here are a few lessons they shared from that experience:
Body language and eye contact
McCollum said he memorized his remarks and focused on his presentation and demeanor in front of the Senate.
"When I gave it, I wasn't reading it, it was there in front of me as a prop," he said. "I was making eye contact with senators. Body language conveys a lot."
"You've got to be focused, disciplined, not distracted by other things," McCollum added.
Several of the current House impeachment managers -- and members of President Donald Trump's defense team -- appeared to approach their remarks on the floor the same way Tuesday.
Reps. Adam Schiff. D-Calif., and Hakeem Jeffries, D-N.Y., barely glanced down at their notes and appeared to speak extemporaneously, off-the-cuff.
Jay Sekulow, Trump's personal attorney who is leading the defense team with White House counsel Pat Cipollone, did the same in his more limited time speaking Tuesday. He also appeared to focus on making eye contact with the senators sitting in the chamber.
Fielding questions will be most difficult part of trial
In 1999, the biggest challenge for former Rep. Chris Cannon, R-Utah, was "putting together a coherent case in a situation where the chief justice is reading questions from witnesses."
The Trump impeachment trial is expected to move to questions early next week, depending on how much time is spent on opening arguments.
They could break it up to different players, but it's really hard to prepare for that other than divide up issues among yourself," he said. "Those guys are going to have to speak on the spot."
Don't get distracted or starstruck
Former Rep. James Rogan, R-Calif., who lost his seat to Schiff in 2000 and now serves as a judge on the California Superior Court, said he felt the weight of history when he walked through the Senate chamber with the other managers ahead of the trial in 1999.
"I was standing on the floor, looking at the big robotic camera on the wall, and thought to myself, 'Let me see, I'm going to try a case, the president is my defendant, the chief justice is the trial judge, I'll be live on television worldwide, the Senate is the jury," he told ABC News. "If I say anything remotely stupid, my great grandkids get to watch it on the History Channel. No pressure!'"
He recalled nearly losing his composure during the arguments when he looked up from the dais and saw the Supreme Court justices and Whoopi Goldberg, who is a co-host on ABC's "The View," watching from the gallery.
Sen. Ted Kennedy, D-Mass., was staring him down intently from his desk and he said it brought him back to his childhood in San Francisco when he cut class with a few friends to wait outside ABC affiliate KGO to catch a glimpse of the young senator and potential presidential candidate. Kennedy took a photo with Rogan and his friends.
"I looked up and had a flashback to him getting out of the car and remembered how thrilled and speechless I was," he said. "And then I remember thinking -- get back to business!"