You need to understand what doubt is better. It’s not a thing that goes away. It’s a quality, that’s mostly negative, but in rare occasions can seem like it’s positive, when directed at something evil. Still, it’s not good even then, as there are better ways to deal with unwanted things. I’ll talk about doubt a bit more later on. So it seems like you want it or it’s influence to be reduced.
To answer your question, things that made the virtue of faith grow in me were mostly spiritual experiences of myself and hundreds of people I read or heard about. Not only from God, not always pleasant, but so profound, that actually the problem seems to invert, and people usually start doubting rather if it’s worth to do anything in the material world, rather than the spiritual one. Of course, until doubt turns it’s barrel on their new way of seeing things
I don’t remember who I was then exactly, but I am sure though that I didn’t acknowledge God’s subtle blessings as a kid, and I definitely had received lots of them. This and some other factors led me on a very bad path for quite a long time. I was taking them as granted, I guess. So I would encourage you to acknowledge, that you probably have or had things in your life or in you, which are not “normal” for everyone and may be influences of your surroundings, your nature, God, devil, and many other factors. It may even be subtle feelings that are there in your life, of being safe, or of the world seeming peaceful… We don’t appreciate those, until we lose them. Then, when we are deep in the satan’s playground, it’s hard to get out, and everything seems so difficult, so complicated, we try to find a solution on our own, not realizing we are no longer able to get out alone, and that we lost a lot of beautiful gifts we received. Only God can help then.
How you perceive the world is unique. That’s why people take comfort in intellect so much, because that’s the common ground where they can relate. They establish common beliefs, points of view, certain unwritten rules and attach themselves to it and find comfort there. Anyways… intellect doesn’t really matter that much, if you want to deal with the problem of doubt.
I hope I’m not prideful while saying that, but I’m completely sure even after a dozen spiritual experiences from God you would still be doubtful! I mean… it hunts me every time I share some spiritual thoughts, now too. This is because you are not fighting with yourself here only. Doubt is not only a human quality, it’s also one of the most powerful satan’s tool. How do you think the saints dealt with the most brilliant blasphemy that satan threw at them at times of testing? By realizing they are powerless against it, and that only God can help them. So pray for that, that God can help you with doubt, if it’s good for you. Maybe what you are going through is taking you eventually closer to God, so it’s always best to ask God for His will to happen. If it’s meant to go through doubt, it’s always best to invite God by your side.