Faith:

Let's take a minute and talk about Faith. There are three kinds of Faith.

There is a fallen Angel's Faith score. This is essentially the limit of their personal power and a mark of how much they believe in themselves. This is also the most expensive stat to raise in D:tF, and it's because Faith is so useful. For instance, did you know that you can have a number of Lores going equal to your Faith? Certainly, you can only turn on one a turn, but some can be extended for several turns/minutes. Faith can be spent to heal your host body, or activate a particularly powerful Lore, or instantly go into your Apoc form. As long as you have a single Faith point in your pool, all of your innate powers function as they should as well.  

The second kind of Faith is the expendable Faith points. These are largely only something that creatures the magnitude of Fallen can utilize, but they can be offered by humans. Fallen (unlike Earthbound, which operate differently) can take Faith from humans in one of two ways. They can reap it, or they can have it offered to them. In a reaping, a person isn't really harmed, in spite of the name, but they must be wow-ed in some way by the majesty and splendor (or terrified beyond reason) of the Fallen. It's hard to orchestrate, but there are Lores that help with that sort of thing. To have humans offer Faith, they need to be offered a Pact by a Fallen. A Pact is an agreement wherein, the Fallen agrees to do a service for the mortal and the mortal agrees to worship the Fallen in turn. Generally, this can't be for something as mundane as like 'give me a million dollars', but if circumstances were dire enough, it's possible that could be an acceptable bargain. The big thing is that whatever is offered needs to be something that the human appears to be incapable of doing on their own.

The final kind of Faith (and point of fact, the most common) is the Faith Potential of a mortal. This is scaled 1-5 and it's important to note that low Faith Potentials doesn't necessarily mean a broken or soul crushed mortal, but it probably does indicate a healthy dose of cynicism and jaded outlook on life. A low Faith potential is generally someone who doesn't believe in things they can't see. The world has proven to be a largely terrible place and they don't see any positive evidence of God's Hand in Creation. A high Faith Potential is someone that is very willing to believe, someone that sees miracles in the everyday and has either accepted that God's Plan is working just fine, or is very ready to believe that idea. It is possible, though difficult for a mortal to raise their Faith Potential. Specifically, being around things that reinforce the idea of a Divine Order will help a great deal (read: Fallen doing Fallen-y things). It's important to note that no religion is accurate in it's depiction of God or the Fall of the Angels, as such, even religions that are kind of close (like Judaism) are still a looooonnnnggg way from accurate. It isn't important that the mortal believe what REALLY happened, just that they are open to believing anything at all. Faith Potential can exist in Hindu, Buddhist, Christians, even Agnostics if they are truly seeking answers.

I have added an XP track on how to raise Faith Potential for mortals (taken from the Damned and Deceived book).