Don’t be that girl
This is a cardinal rule of adulthood, and it bears repeating here. Part of what makes tailgating so much fun is the communal effort involved - everyone coming together to create a good time for all (you bring the drinks, I’ll do the grilling, he’ll pack the chairs, etc.). So get involved, participate, and do your fair share.
Express gratitude to those doing the heavy lifting (yes, loading that grill onto a truck is much harder than it looks), and offer to contribute something to the festivities. Don’t be that girl who shows up empty handed, helps herself to the free drinks, and leaves without a word of thanks. If your invite is truly last minute, pick up a bag of ice on the way. Tailgates always need more ice.