Back when I lived in the Los Angeles area, I'd be able to get korean ginseng at a fairly good discount and munch on them like potato chips throughout the day. This was back when I felt at my physical and energetic peak.
Since then I'd try out some of the various pills that you can find in supermarkets, health & drugstores. Although there were similiar benefits, none of them FELT as strong.
Now I live near Wisconsin, so I'll be looking around for good deals on american ginseng (grown in wisconsin) and go back to munching on them like chips throughout the day.
NOTE: the older the ginseng when harvested, supposedly, the stronger the properties (and more expensive per unit). The ginseng I would munch on were typically younger than 6 years.