You will need at least a pound of elderberries for this recipe, and preferably three pounds, so you have enough to last a while. I use a food mill to extract as much juice as I can from the berries, but if you don't have one you can use a jelly bag. I am pretty cavalier about my canning practices with syrups, as they are so sugar-dense they are incredibly resistant to bacteria. I don't bother to sterilize my equipment, although I do make sure everything is freshly cleaned, and I do use a brand-new canning lid. If you feel the need to process your syrup in a boiling-water bath, 10 minutes will be more than enough.
NOTE: Elderberry syrup is best kept refrigerated. It will last a year this way.