Atelier Rorona: The Alchemist of Arland

Trust Level is basically your Town Popularity. Similar to the Friend Requests, Popularity is gained by completing requests offered by Esty in the Palace. The difference between them however, is that these Front Requests gets replaced every day.

Most of what she asks will be things you can simply buy from the stores, as well as simple items you find when traversing dungeons, such as Puniballs. She'll often ask you to create certain items, but they're not worth the time and effort. Simply make a habit of checking up on her everyday, completing requests that you can buy from stores, and you'll reach 100% in no time.

As you progress through the game, she'll start offering you bounties, which requires you to travel to a specific dungeon and slain them. Contemplate before accepting them to make sure you can defeat them. Note that these aren't missable, but are just simply hard to get specific ones to appear. You can keep reloading and saving till she offers them during clean up, but I advise you to complete them ASAP if possible.

As mentioned in the Road Map and Walkthrough, it is advised you reach only 80%, so you can lower or raise it to get the different endings. Once you're at 80%, consider making a save, do requests till you reach 100% to earn the trophy, then reload the previous save to continue what you were doing.