It is important to add the ingredients in the correct order. Don't over-fill the glass. Use a decent bottle of Champagne. You don't need to use the best Champagne. Mixing an expensive bottle of Champagne with brandy is a bit of a shame and rediculously extravagant, unless you really feel the need to impress someone and don't really respcect the bubbly. But you don't want to use the cheap stuff either. That's like putting lipstick on a pig. There is nothing you can do; it's still a cheap bottle of sparkling wine. Use a good brandy. It is always best to use a proper flute when drinking Champagne.