The question of how to know Truth is a fundamental question of philosophy. Truth with a capital T has been debated and sought after by every philosopher pretty much ever. In everyday life we do this too. The joke, "I saw it on TV, it must be true!", or simply asking how somebody knows what they're talking about. In arguing politics, God, or various other uncouth dinner conversations we'll reference a class, a life experience, a book we read. We'll talk about how we were raised, what's acceptable, and why it's acceptable. This is the every day man's search for Truth, and it's similar to any philosopher's search for Truth, it's just not published (though I don't want to denigrate the expertise of those who study philosophy -- I just think we, on a day-to-day basis, loose contact with the fact that we're essentially answering the same questions, only in different ways, and possibly at different levels of understanding).
So, how do we know Truth? That is the spawn of a lengthy discussion and inner dialogue, one in which I am still looking for. However, there is a misconception about science that I think is very important to understanding it -- that science is truth. Or, more importantly, the misconception that scientists think science is truth, but the rest of the world knows it's just science. So, without further ado, here's a quick run-down of what I think of the interplay between science and truth.
1) "Just" Science
To be clear, I am not speaking out against the scientific method in the least. It is, in my opinion, the most surefire epistemic method for understanding the natural world. There are a few assumptions made in scientific inquiry, but that's alright -- we need to make assumptions in order to come closer to truth. In the days of Euclid, mathematicians were trying to go about proving everything, and it was he who said, "Fuck proving that lines are straight -- they just are" (roughly). He said a number of other things related to geometry, but aside from his enormous contribution to mathematics, he also made an enormous contribution to logic: Not everything can be proven. In fact, one has to accept certain propositions in order to move on and build. That's what science does -- makes a few assumptions that really are not terribly controversial, and builds a knowledge of the natural world using them.
EDIT: I need to admit a mistake. Aristotle actually points out that one needs to start from some point in order to build a system, and he is dated older than Euclid. I'm not sure if any Pre-Socratics pointed this out, as well, but this at least pushes the date further back, and as Aristotle is the first person to give a strictly formal account of logic, it wouldn't be surprising if he's the first to point out this feature.
2) Science, and truth
So, we gain a knowledge of the natural world. But what exactly does this knowledge entail? How do we KNOW (in uber-skeptic parlance) that what we deduce in scientific inquiry is true? Well, strictly speaking, we don't. Science proves nothing. Technically, science only disproves things. The fact remains that, even given that we discover everything in the universe, we will not know if we have discovered everything in the universe. There can always be something else -- it's how science grows. We notice something, and attempt to come up with a reasonable explanation and description of that something. We test that description, and if everything matches up, declare that our description is good. The problem is, this is not always the case. It was probably a good description. Maybe there were some implicit assumptions in our description we didn't realize. Maybe we hadn't encountered a certain element just yet, due to our inability to detect a more subtle feature of the world, or due to that elements scarcity. So, while scientific inquiry deduces good explanations of the natural world, they are not the capital "T" Truth truths that we know, in an absolute sense, are true. They're just damn good approximations of Truth.
3) The limitation of truth in the natural world
So, what're we to do? Well, science is about it, when it comes to the natural world. Unless you're taking up the philosophical banner of absolute relativism, or have recently been convinced of Epicurus' physics, the natural world follows laws (again, rough). Our formulation of those laws may be off, but that doesn't change them existing. We, human beings, are not naturally in tune to these laws, can not deduce them from pure thought, and need to test the universe to understand them.
4) So, how do we find Truth?
Good question! It's one I think about myself. Supposedly, you could reach truth if you have a valid argument and all of the propositions in it are true. But there's no way of telling if your propositions are true. It's intuitive. It's subjective. And as Truth doesn't change (well, I guess that depends on who you ask), but we change all the time, we could know truth and not know that we knew it, and change again in pursuit of the elusive ends of our questioning. It's actually what Plato talks about in his "Symposium" -- it is the lot of the philosopher, the lover of wisdom (and therefore truth) to love and pursue wisdom, but he can never know it, only search.
So, in closing, while the scientific method shouldn't be applied to all areas of life -- that'd be mildly rediculous -- I think settling for approximations of truth ain't too bad a deal.