Be visible. Wear reflective clothing for nighttime visibility, but don’t forget the bright neons to be seen during the daytime. Either neon raingear or neon mesh (or both) will be a good idea.
When you ride in a group, ride with people you know and trust. If you’re not sure, ride alone. The last thing you want is to be is sharing a lane with someone who’s loaded, or showing off, or just plain ignorant. If you get into a group and it starts to go faster than you’re comfortable with, it’s okay to hang back. Go your own speed. The roads outside of Sturgis, the scenic ones, are twisty; why be in a hurry? The speed limits are maximums; you don’t have to go that fast.
Take breaks—either after so many miles or after so many minutes. Stretch your legs, flex your hands, and enjoy the views.
Stay safe out there!