Pouring it down the side of the glass is indeed the best method.
The first sentence of the abstract reads… “Pouring champagne into a glass is far from being consequenceless with regard to its dissolved CO2 concentration”.
“On the Losses of Dissolved CO2 during Champagne Serving”. Gerard Liger-Belair, Marielle Bourget, Sandra Villaume, Philippe Jeandet, Herv Pron, Guillaume Polidori. Journal of Agricultural and Food Chemistry 2010 58 (15), 8768-8775
“Figure 3. Time-sequences illustrating both ways of serving 100 mL of champagne into the flute: the champagne-like way of serving (this way is the traditional way of serving champagne and sparkling wines in bars, clubs, and restaurants) (a) and the beer-like way of serving, traditionally reserved for serving beer (to prevent an excessive formation of foam) (b). (Photography by Grard Liger-Belair.)”