This is the way leading to discernment: when visiting a brahman or contemplative, to ask: ‘What is skillful, venerable sir? What is unskillful? What is blameworthy? What is blameless? What should be cultivated? What should not be cultivated? What, when I do it, will be for my long-term harm & suffering? Or what, when I do it, will be for my long-term welfare & happiness?’
— from MN 135, translated by Thanissaro Bhikkhu (http://www.accesstoinsight.org/lib/study/merit.html)
When the Buddha lived (~500BCE), books were extremely rare. They might have been etchings on palm leaves that hardly anyone could read. So when the Buddha encourages us to visit a wise person and inquire about good guidelines to live by, that was pretty much the only avenue open to an ordinary person at the time. It’s still good advice, because having a living teacher in front of us can be a powerful experience. However, the wisdom of the ages is also now readily available to everyone, through books and other sources.
If we are trying to figure out the best way to live (and perhaps investigate some related questions, like why we suffer), we are faced with the difficult task of identifying which advice is wise and which is not.
The Buddha was an empiricist; he often stated that we should try things out and see the results for ourselves. So, we turn our attention to studying which of our actions cause problems and which turn out well, for ourselves and others. This is a most accessible and useful form of meditation.
The main guidelines the Buddha offered for our testing were the five precepts: harmlessness, generosity, restraint in sensuality, truthfulness, and sobriety. These are the foundations of all spiritual progress, and their regular practice brings a sustainable sense of wellbeing, even joy.
An additional instruction is contained in the paragraph above: we should be alert to who we consider wise and who we consider foolish, and seek out and listen to the wise. If we actively pursue teachers and others who bring out the best in us, either by their words or by their example, we’ll be on the right path. If we make no effort to choose whom we spend our time with (in person or in books or other media), we’re likely to go around in circles.