I'm trying to make the perfect Egg Cream, which requires maximum carbonation. Should I shake the bottle before opening it?
What will help is chilling the soda water as much as possible. Gas is more soluble in water at lower temperatures, and the difference is appreciable over a relevant range (drinks fridge at 8C vs the coldest part of your fridge at 2C). Be sure to leave it long enough that it's well and truly cold, and handle gently.