Recently I've been starting my workouts with (after warm ups) a few sets with 50's - 55's on a low incline dumbell curl for 6-10 slow reps, focusing on just squeezing the bicep. Then higher reps on barbell curls and machine curls with similar form.
If you want to show how much you can lift- full squats, deads, benches, overheads, in good form. Worrying about curl poundage is ridiculous and usually leads to shitty form.