We've all done the dumbbell curl, but if you're actually attempting to isolate your biceps a little better (when I say "better", I mean "without cheating as much"), then I completely recommend trying out the incline dumbbell curl. Here's how it's done:
Locate the incline seat at your gym; it will generally be its own thing, but sometimes you'll need to really pull the pin out and raise the standard seat yourself. Sit down on it with a dumbbell in each hand. (If this is your first time going it, then I recommend starting with about five pound less in each hand then you would normally do with the regular Dumbbell Curl) Beginning with your arms hanging loosely down by your sides.
As always, remember to keep your elbows close to your sides and just in front of your body (torso). Slowly start to lift both arms - at exactly the same time - in the ordinary motion of curling, and cease when you can not lift them up any higher. Be sure to keep your arms balanced and as steady as you can while doing this face lift.
Pause when you get to the top of the elevator, then slowly lower your arms back down to where you started.
At the base, count to three to three and a half before beginning another repetition. This should keep you from depending on the impetus of your arms to swing the dumbbells back up.
If done right, this really should minimize cheating, thus giving yourself a much better workout.