Apparently elderberries contain high amounts of vitamins and anti-oxydants. If you can find yourself a good area where elderberry bushes grow, they are really easy to pick. Elderberry bushes usually grow in overgrow areas, parks, country roads etc...it's best to find some where off the road as pollution can find its way into the plant or onto the berries, which I've heard isn't very good (surely the plant filters the pollution out through photosynthesis?? Sorry I'm not a biologist, I don't really know) either way, it's nicer to have a walk off the road to pick them.
The berries are dark almost black, like the colour of blackberries and come in clusters of tiny berries. Make sure you know what you're picking before you pick anything and eat it!
You can easily pick them by cutting the whole cluster off, then when you bring them home you can pick the berries off the clusters.
Some people like to use a fork to 'comb' them off, I found it good to gently tease the berries of the stalks. Then I washed them carefully, trying not to squish them all and put them in the freezer for a later date.
I love these tiny berries, they are like a tastier less seedy version of blackberries, a nice addition to an apple pie!