I always start by putting the juice, club soda, and grenadine in the refrigerator a few hours before my party. A punch that's already cold tastes so much better than one I'm trying to chill down with ice at the last minute. This step takes zero effort, just a little planning ahead.
In my punch bowl, I pour in the berry juice first, then slowly stir in the grenadine. Watching the grenadine swirl through the juice and turn it a darker, richer red is honestly half the fun of making this drink. I stir gently so I don't lose the color effect too quickly.
Right before I'm ready to serve, I pour in the cold club soda and give everything one light stir. I add this last so the punch stays as fizzy as possible instead of going flat while it sits out. This is the step that turns a simple juice mix into a proper party punch.
I always serve this punch cold but without ice cubes floating in the bowl, since melted ice dilutes the flavor and washes out that deep red color. I keep the punch bowl over a bed of ice instead, which keeps everything chilled without watering it down. This little trick makes a noticeable difference in taste.