Today at the gym I switched it up a bit. Instead of three sets of 10 reps each, increasing the weight each time, I went for three sets of 18 reps each, keeping the weight the same.
I did the overhead press, and then shoulder shrugs. Holy. Crap. I'm soooo gassed from the workout! Normally I do three different exercises, but with the extra reps I thought two was okay. And I still do. My shoulders are cooked, and I'm looking forward to tomorrow with a bit of fear - they're gonna be so sore!