Even if you've studied something like biology or nutrition it's incredibly difficult to judge what is good and what is bad advice, as your average school (and professor) is just as full of dogma that has only the most tenuous basis of evidence.

Far and wide the best ground advice you can give yourself and others is to work out - that'll do good things to you, even if you can do it a little. Other than that, eat a moderately varied set of foods. Anything further than that is usually just something someone came up with in the shower and that other people thought sounded real good.