If you are only serving a few glasses of Champagne, it is easiest to tilt the glass first, as you would when pouring a beer, so that when you pour it, the glass doesn’t overflow with froth.  But if you are pouring Champagne for a big party, it is best to first pour a little of bubbly into each glass, to fill by one-third; then as soon as the froth has died down, top up the glasses.  If it looks as if the foam will shoot over the top of the glass, quickly put your finger in the middle of the foam or dip the end of a teaspoon handle in the middle.