1. Golarion has a less simplistic viewpoint than some other dnd settings - i'd compare it to Eberron more than I would Faerun or Greyhawk. Different pantheons are worshiped, certain deities are popular in certain countries and regions, certain countries are religious, and certain countries are, well, the opposite. It's closer to a setting like the Malazan Book of the Fallen books than Medieval Europe, so, more 'fantastical'. People pay lip service to gods, and true believers are relatively rare compared to people with more mundane concerns. Gods aren't there to be believed in - they're there to be worshiped for magical power, or opposed. Sort of like a belief-based pyramid scheme.
A manner in which it does echo faerun and the like though, is that the Gods are accepted as real. 'Atheists' are rare or nonexistent, although those who dislike the Gods aren't necessarily so. Clerical magic is accepted to be a gift from the gods, and when something large-scale occurs, 'a god did it' is a reasonable response.
Keep in mind though, the idea that God/the Gods are infallible also isn't a part of the common cultural mindset. They are inherently fallible beings in the setting, just like mortals. So being sure of your god's will and infallibility is a sign of fanatacism, and not the status quo (as it is supposed to be with the abrahamaic religions of our world).
This is important, because you are playing a fanatic.
2. You're a Paladin. You are someone who believes in a god to a greater extent than someone who can summon angels from heaven with their faith. You are a living exemplar of your God's path. In short, you're a fanatic. You're a fanatic of Good, and Law, (unless you're playing an Antipaladin), but that's still a form of fanaticism.
And that's where you find inspiration. Fanatics of God in the real world act in specific manners - even those not enmeshed in a religion but rather something else like a way of life ('fitness fanatics''fanboys''conspiracy theorists'). Believing utterly in something causes a number of specific behaviours, all of which can act as inspiration to you in playing your character.
Immune to Fear - With faith, all obstacles in your path are surmountable. Unflinching is hard to portray as most PCs usually never show fear (often also any other emotion, being great and terrible murderhobos made of carnage as they are), so a lack of it isn't especially notable. So, describe it as glee. The next step beyond 'unflinching' is 'filled with unholy glee at the prospect of danger'. So go to that. A demon scuttles out of the shadows, hisses at the group, and your paladin grins and thanks his god. The villager tells fearfully of a dragon, and your paladin is filled with huge need to challenge it, tales of it's huge size and magical fire breath only firing his ardor. Caution: May cause heroic, epic, awesome paladin death. Note: Doesn't mean 'never runs away', just is excited by danger.
I'm Blessed, and you're Not - You're a devout follower of your God, who is the best God. Other gods' worshipers who are aligned with your God might get a bit of respect, but not people, especially those who flaunt their impiety instead of bowing their head in proper respect to the Lord of Song/whatever. Prissy, self-righteous, self-important, respectful to clergy but not to anyone else, and basically a bit of a prick. The negative side of moral conviction, and instantly identifiable from anyone who's had to deal with religious fundamentalists in a modern western sense.
Noble - 'Leading by example' is hard to portray in DnD, but this is the Positive form of moral conviction. You'll need a GM who sets up opportunity to take the hard path and show internal conflict that you can resolve with willpower and stoicism. The idea is that you hold yourself to a higher standard than anyone else, in order to serve your god, without necessarily judging everyone else as wicked and evil. This is basically the 'standard paladin' schtick.
Don't you understand? The answer to all life's problems is in this book written thousands of years ago! - Evangelism purports to be a modern invention but it is in fact very old. The problem is, all these people just don't realize that they NEED the Lord of Song. And they need him like, right now, in their lives. And if they would just listen, then hell, everything would be okay. Right as rain. Right as song, even. This is a recurring theme in your character's life. Other people just not getting it. Fighting monsters who don't get it, even. Any activity that is not in some way convincing people to worship the Lord of Song is clearly a waste of time, and every time people don't take the opportunity to join you in prayer/song, well, that's just bloody frustrating, innit.