Truth is reality. If something is, it is true. For example, I watered my garden yesterday. That is true. I actually did. Whether or not you believe me, it remains true. For those of you who didn't see me water my garden, you'll have to trust me. If there is someone you do not trust, then you cannot trust that they speak truth. You can trust someone who has proven themselves to be an honest person.
If you are wanting to know the truth of ideas, consider from whom the ideas are coming. Again, if you trust their judgment, you can trust that they may be right . . . but maybe they are not. Even someone you trust will say things that are not true. It is not because they are being deceitful; they believe that what they say is true. So, each person has to find out for themselves what is true and what is not. For some things, it's easy. The water is cold - that's what you've been told. Well, you can find out for yourself by putting your foot in the water. If it's cold, it's cold - truth. You can go deeper and define what cold is with a temperature, and still you can say whether or not it's true, according to the definition that has been set for what constitutes "cold" water. Other things will be harder to find out. For example, someone tells you what it takes to lose 50 pounds. Following their advice, it may take 6 months or longer before you know for sure if what they said is true.

And still, some truths may take a lifetime before you can say that you know they are true.
I also agree about a feeling/voice that speaks to us when we hear truth. If you are sincerely and actively seeking out truth, then that feeling will help you to discern it. It's different than feeling resolute about something you wish to be true. Also, sometimes we know something is wrong, and that feeling leads us to feel uneasy and then to seek truth in the matter.