How to use barter?

So, how does one actually go about using barter in today's world? It seems like a concept that's been around for centuries, but how can it be applied in our modern, digital age? Do we simply find someone who has something we want and offer them something in return, or is there more to it? How do we determine the value of what we're offering and what we're receiving? And what are some potential pitfalls or challenges that come with using barter as a form of exchange?