Even though measuring from cranial landmarks is one way to find these points, I always question measuring on the head, or body, because of the size differences between people. Hence to make it easier to locate the points, below are numerous pictures.
Left Anode Dorsolateral Prefrontal Cortex (DLPFC)
The left is obviously the left side of the head, and the anode is the more positive of the two leads (green wire on the Cognitive kit); current goes from electronics to anode through the head to cathode back to the electronics. For the position of the DLPFC, check out the cranium below:
And on me pointing and with a sponge electrode(see there is an advantage to having little hair, better tDCS montage location and better electrode connection).