Marshrutnis minibuses from Yerevan are inexpensive and will take you to Vanadzor in a couple of hours. They depart from Kino Rosia, above the Zoravor Andranik metro station, across from the national cathedral. Shared taxis leave from the same spot, and are a bit more comfortable, fast and a little more expensive. Virtually any taxi in Yerevan will take you there for 100drams/km 33cents US, which adds up to about 12,500 dram, unless you're a good negotiator.