According to my Nutrition professor, it's really hard to tell what's good and what's not. Reason being is that the herbal supplements are unregulated (at least in America) and manufacturers can make false claims about their products. It's a shame too. We are often literally pissing our money away (sorry). Vitamins are regulated but there is a danger of toxicity with fat soluble vitamins, b vitamins and trace mineral. The best information you can get about supplements would be from peer-reviewed science journals or even http://www.webmd.com/ . And I'd suggest talking to a Nutritionist before choosing something because there's a good chance you can get it from your diet and there's a small chance that taking multiple things could cancel out postive nutrient functions.
I hope that's not too preachy. Its just fresh in my mind from this semester!!