I just do single arm bicep curls with free dumb bells. The key really is mostly in the form. I see people swinging the weights around like idiots and all that is working out is the laws of physics. Shoulders slightly back and elevated. Do not move your shoulders one fucking bit. Tuck your elbow onto your rib cage. Again this does not move. Full extend your elbow downward with the weight. Curl up. Finish the curl by curling your wrist forward as well. This will work out your forearm and your bicep as well. Another trick is do not hold the dumb bell in the center. Rather hold it so the outside of your hand is touching the weight (basically the weight is unequally distributed towards the outside of your body) and this will strain your bicep even more.
I can't say I'm an expert but it works out well for me. I generally curl 40lbs until thats exhausting, 35 then 30. I just repeat that. Probably about 5x per arm at 40, 5x per arm at 35 then about 10x per arm at 30 per set. Then at the end of the workout I burnout with as many hammer curls as possible at 30lbs. A little trick I've come up with for doing my hammer curls is I actually slowly walk around while doing them. It takes my mind off the exhaustion and if I'm further away from where I rack the weights I can't just easily put them down.
Heres me maybe a year ago. I've really been working on getting my biceps back in shape. If you don't have the gross vein while your biceps are resting you aren't working on it hard enough!
(Also bonus shots of my 1year old faded PBJ 24-005's!)