Remember back in the first episode when the journal told Dipper to "trust no one?" Well, let's take a look into each episode. We'll look at who the characters trusted (and didn't trust) and how it turned out for them. Red means it backfired horribly, green means it paid off, and yellow means I'm not sure.
1: Mabel didn't trust Dipper's warnings about Paranorman. At the very end, Dipper trusted Mabel when they were cornered by the gnomes.
2: Dipper, Mabel and Soos trusted Old Man McGucket about the Gobblewonker over Stan.
3: Blubs and Durland didn't trust Dipper and Mabel.
4: Mabel trusted Gideon. Dipper, however, did not.
5: Dipper and Mabel trusted Wendy and her friends that they would be fine. And, nobody trusted Dipper's warnings about the ghosts.
6: Dipper trusted the Manotaurs about his manliness. In the B-plot, Stan trusted Mabel to help him get a date.
7: Dipper trusted his own good intentions when making his clones.
8: Dipper trusted his own instincts over Mabel. They both trusted Quentin Trembley at the end.
9: Dipper trusted his plan to upstage Robbie over the natural order of things.
10: Again, Dipper trusted his plan to destroy Robbie over the natural order of things. Also, Stan trusted Mabel to get him over his fear of heights.
11: Dipper, Mabel and Stan all distrusted Gideon. But, Stan also distrusted the Winninghouse Coupon Savers Contest people.
12: Once again, Dipper trusted his own plan to win Wendy's heart. Also, Stan trusted his own skills as Stan Pines, Master of Fright!
13: Dipper, Mabel, and Soos trusted in their own skills at running the Shack over those of Stan. Meanwhile, Stan trusted his own skills on Cash Wheel.
14a: Dipper trusted McGucket over his own family and friends.
14b: Dipper and Mabel trusted Soos to save their lives.
14c: Mabel trusted her own judgement that the truth is always a good thing.
15: Yet again, Dipper trusted his own plan for himself and Wendy, ignoring his sister in the process. Also, Stan trusted his own skills against Gideon.
16: Dipper and Mabel didn't trust each other to stay in the same room together.
17: For the umpteenth time, Dipper trusted his own judgement in what the summer should be. Also, Sev'ral Timez trusted Mabel over Candy and Grenda.
18: Mabel refused to trust Stan, and Dipper refused to trust Soos. That is, up until the end.
19: Dipper had serious trust issues with Stan.
20: Dipper and Mabel didn't trust in anything for most of the episode. They trusted in each other near the end. And of course, they trusted Stan at the very end with the journal.
Shorts 1: I honestly couldn't think of anything.
2: Dipper trusted his own judgement over Stan.
3: Dipper and Soos trusted the mailbox.
4: Dipper distrusted the Lefty robot.
5: Dipper distrusted Bear-O.
6: Dipper trusted Lazy Susan and Manly Dan over Stan about the Hide Behind.
7: Dipper, Soos and Stan trusted Mabel with her dating quiz.
8: Mabel distrusted Dipper's warnings about the sprinkles. (If this was a full-length episode it probably would have backfired.)
9: Stan, Soos and McGucket trusted Mabel's flash makeovers. (OK, that's a bit of a stretch.)
10: Mabel trusted her own judgement about Stan's dislike of color.
11: Stan trusted in Mabel's art skills.
12-13: Dipper, Wendy and Stan trusted Soos's fix-it powers.
14a-b: nothing
14c: The other prisoners trusted Gideon.
15a-b-c: nothing
16: Dipper, Mabel, Stan and Soos trusted each other's skills to get into the theater.
17: I tried to come up with something... and failed.
2.1: Dipper trusted the government agents over Mabel and Stan.
2: Mabel trusted her own good judgement over her common sense about the dangers in the bunker.
3: Dipper and Mabel trusted the Lilliputtians to help them beat Pacifica without killing her.
4: Mabel trusted Gabe and Dipper trusted Bill.
5: Soos trusted Melody over Giffany.
6a: Stan trusted his heisting hands over the Hand Witch's and Dipper's warnings.
6b: Dipper and Mabel both trusted that Waddles was happier as their best friend.
6c: Mabel distrusted Stan, Dipper and Soos that stop motion is fake.
7: Dipper, Mabel, Stan and Soos trusted McGucket as they defeated the Blind Eye Society.
8: Blendin trusted his own skills against Dipper and Mabel. Soos, however, trusted the kids. And young Soos trusted his dad (early on) and Stan (at the very end.)
9: Robbie trusted Mabel with his broken heart.
10: Pacifica trusted Dipper to save her family from the ghost. Later, Dipper trusted the ghost over Pacifica.
11: (Dipper) Mabel, that thing could destroy the universe! Listen to your head!
(Mabel) Grunkle Stan... I trust you!
Here is the predominant trend that I noticed. When our protagonists trust each other, they typically come out on top. But when they trust anyone else, including themself, it tends to backfire horribly.
"Grunkle Stan... I trust you!"
Need I say more?
