We have all done the dumbbell curl, but if you're really trying 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 is done:
Find the incline seat at your health club; it'll usually be its own matter, but occasionally you will need to actually pull the pin out and raise the ordinary bench yourself. Sit down on it with a dumbbell in each hand. (If this is your very first time going it, then I recommend starting with about five pound less in each hand then you'd ordinarily do with the regular Dumbbell Curl) Beginning with your arms hanging loosely down by your sides.
As always, be sure to keep your elbows close to your sides and only in front of your body (torso). Slowly start to lift both arms - at the same time - in the regular 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 began.
At the base, count to three to three and a half before beginning another repeat. This should keep you from depending on the momentum of your arms to swing the dumbbells back up.
If done correctly, this actually should minimize cheating, therefore giving yourself a much better work out.