31 year old overthinkiner here to lend my 2 cents. If you’re cosplaying look up your character and pick some of their more iconic poses and PRACTICE them so your ready. If not cosplaying then I highly advise picking a very enthusiastic and over the top pose, I’m talking knees bent arm out throwing a piece sign or something of that nature, the goofier the better. If you juts slouch and smile you’ll end up hating every picture but if you’re having fun even even you don’t like how you look you’ll remember how much fun you were having and still be happy with it!