There are plenty of opportunities to meet the requirements for this trophy just playing through the game however I wanted to mention the way I use that gets all 3 in just a few minutes at the very beginning of the game and seem to be guaranteed successes at both persuading and intimidating regardless of Speech skill.
This method requires going through the first 2 Dark Brotherhood quests, Innocence Lost and With Friends Like These...
1. Travel to Windhelm and talk with Aventus Arentino and he'll send you to Riften.
2. At Riften either Persuade, Bribe or Intimidate the gate guard. Persuade and Intimidate options are not guaranteed to work. Once inside you'll be stopped by Maul, Bribe him. Complete Aventus' task and return to him.
3. Sleep in a bed somewhere other than Riften.
4. You'll wake up in a cabin, go through a bit of dialogue and have the option to question 3 people. They each have a Persuade and Intimidate option that seem to have a 100% success rate regardless of Speech skill.
5. Trophy unlocked.
If there is any way that I can make this solution better please don't hesitate to let me know.