I keep a bottle of elderberry tincture around and have found that if Mr. G and I take a spoonful at the first sign of a scratchy throat or flu-like symptoms, it seems to keep whatever we were coming down with at bay. We've gone several years now without suffering the flu or even a major cold. It may not work for everyone and shouldn't be considered as a replacement for traditional flu preventatives and medications, but it has worked well for us so far.
A few years ago we would gather wild elderberries, but it was often difficult to get to the berries before other critters had harvested them, so I ordered an elderberry bush from Possum Creek Herb Farm. It has grown like wildfire, and is a lovely sight in May and June when it is in full bloom. I sometimes gather and dry the elder flowers to make elderberry tea, which is quite delicious sweetened with local honey.
Once the jar is filled, I cap it and place it in a dark cupboard for about 2 months. I try to shake or turn the jar at least once a day, since it seems to help speed up the extraction process, but I don't think it's crucial and have been known to skip several days without dire consequences.
So we have been feeling fine this flu season with our tincture, but I may be lucky enough to have a bumper crop of berries this summer. Maybe even enough to make a tincture AND some elderberry wine. Then we can sing "Elderberry Wine" along with Elton John :-)