First off the EVSE is usually hard wired if you are using a 240 volt station so you wouldn't need the plug at all. If you want to plug it in though refer to the Code.
The 2011 NEC does not allow you to do this at all for anything but a 120 volt system.
625.13 Electric Vehicle Supply Equipment. Electric vehicle supply equipment rated at 125 volts, single phase, 15 or 20 amperes or part of a system identified and listed as suitable for the purpose and meeting the requirements of 625.18, 625.19, and 625.29 shall be permitted to be cord-and-plug- connected. All other electric vehicle supply equipment shall be permanently connected and fastened in place. This equipment shall have no exposed live parts.
The 2014 NEC allows you to do it with conditions:
625.44 Electric Vehicle Supply Equipment Connection. Electric vehicle supply equipment shall be permitted to be cord- and plug-connected to the premises wiring system in accordance with one of the following:
(A) Connections to 125-Volt, Single-Phase, 15- and 20-Ampere Receptacle Outlets. Electric vehicle supply equipment intended for connection to nonlocking, 2-pole, 3-wire grounding-type receptacle outlets rated at 125 V, single phase, 15 and 20 amperes or from a supply of less than 50 volts dc.
(B) Connections to Other Receptacle Outlets. Electric vehicle supply equipment that is rated 250 V maximum and complying with all of the following:
(1) It is intended for connection to nonlocking, 2-pole, 3-wire and 3-pole, 4-wire, grounding-type receptacle outlets rated not more than 50 amperes.
(2) EVSE is fastened in place to facilitate any of the following:
a. Ready removal for interchange
b. Facilitation of maintenance and repair
c. Repositioning of portable, movable, or EVSE fastened in place
(3) Power-supply cord length for electric vehicle supply equipment fastened in place is limited to 1.8 m (6 ft).
(4) Receptacles are located to avoid physical damage to the flexible cord.
All other electric vehicle supply equipment shall be permanently wired and fastened in place to the supporting surface, a wall, a pole, or other structure. The electric vehicle supply equipment shall have no exposed live parts.
Second, Follow ThreePhaseEel's advice on the ground wire for the circuit. Grounding for a circuit in a garage is especially important.
Third, an EVSE is considered a continuous load so the circuit breaker and wire for an EVSE have to be sized 125% of the ampacity of the load.
Here is a quote from the 2011 code (this is 625.40 in the 2014 code):
625.21 Overcurrent Protection. Overcurrent protection for feeders and branch circuits supplying electric vehicle supply equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the electric vehicle supply equipment. Where noncontinuous loads are supplied from the same feeder or branch circuit, the overcurrent device shall have a rating of not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads.
Good luck and thanks for helping to save the planet!