Two Three Way Switches w 14/2
Most commonly, in a two switch setup, line power comes to the first switch then goes to the second switch and then to the fixture.  

In this setup, you need a three wire cable between the two 3-way switches (we don't count the green or bare ground wire when describing cable). Two of the wires are travelers (alternately serving as the hot line) and the third is the neutral. The hot wire from the line cable in is attached to the common on the first 3-way switch. The neutral from the line in cable is attached to the neutral in the cable to the second switch. At the second switch, the travelers go to the traveler terminals and the hot wire to the fixture cable is attached to the common. The neutral from the traveler cable is attached directly (not through the switch) to the neutral of the fixture cable.

If the second 3-way switch is not between the first switch and the fixture (because there is already a neutral at the fixture), you need at least three wires to the remote switch, two travelers and a return hot line to the fixture. In addition, code now requires a neutral at each switch, so you should have four wire to a remote 3-way (the neutral reserved for devices that may need it in the future).