If you are thinking of making Elderflower champagne, then this is probably a good recipe, though I never put vinegar into anything - can't stand the stuff and won't have it in the house. http://www.channel4.com/food/recipes/chefs/hugh-fearnley-whittingstall/elderflower-champagne-recipe_p_1.html
I was taught to ask the Elder tree for permission before taking any of the flowers. it was said that this would prevent the flowers smelling of cat pee, but the truth is that if you pick flowers in the morning they should smell slightly of bananas, if picked in the afternoon/evening they WILL smell of cat pee. Be warned.
The best Elderflowers are picked when they’re white and newly opened. The older creamy ones are riper and should be avoided. Leave them for the berries and a rich red wine. Don't wash the flowers, just shake them to get rid of insects and pull the flowerets off the stalks. If, like me, you suffer from hay fever, beware the pollen - wear a mask.
Also very beautiful in the hedgerows around the village are the dogroses. lovely to look at and beautifully scented, but beware the thorns. What I want to know is why, if the idea of thorns is to prevent the flowers and leaves being eaten, they all face backwards, so an animal can thrust its muzzle in but not get it out (without consuming everything first).