While buying a battery(LiPo) you should consider these factors ,
C rating :Peak continuous discharge capacity
mAh rating : Battery capacity (how much energy the battery can store)
Battery voltage : This depends upon cell configuration you can chose from single cell (4.2V) , 2S(8.4V) , 3S(12.6V) 4S(16.8V)....
Cell configuration : This is how the cells are arranged inside a battery pack a 3S pack means, 3 cells are connected in series , a 4S1P means 4 cells in series and one cell in parallel to this.
While selecting a battery for any purpose, you should mainly take care that, the battery is of required voltage, the battery can supply sufficient current .
In a multirotor, the total current draw is mainly by 4 rotors (Current draw by other electronics is negligible) . for your quadcopter , your motors runs at 3S and assume each motor's max. current draw is 15A (at full throttle) , so total current draw by motors can be up to 60A . So the battery you select for this quad should be able to contiguously supply more than 60A.
In a LiPo Peak discharge current = C rating x mAh rating (Discharge rating x Battery capacity)
So for a 3S 2200mAh 30C LiPo, Max discharge current = 30C x 2200mAh = 66A - which is little above your requirement, and you can safely use this battery pack.
Key points to note, while purchasing LiPo :
1) Required battery voltage (For your quad, a 3S (12.6V) battery will do)
2) Max. discharge current should be higher than max. current draw by your setup (Quad)
3) Battery capacity (mAh) - this value determines storage capacity of battery higher the value higher the battery capacity, higher the flight time .
4) Weight of battery pack : to say easily battery should be as lite as possible for a most efficient multirotor . Even though high capacity battery provides more flight time, you cant use very high capacity batteries because more the capacity, more the weight of the battery. So you should chose an optimum capacity battery whose weight does not go higher than pulling capacity (Thrust) of your motors (Now calculation of thrust for a multirotor is little different it is not simply add up sum of all the motor's thrust ).
I think i have explained in the min. words possible - so if you don't understand anything, feel free to ask .
Please visit these links :
http://blog.oscarliang.net/how-to-choose-battery-for-quadcopter-multicopter/http://blog.oscarliang.net/build-a-quadcopter-beginners-tutorial-1/http://blog.oscarliang.net/multicopter-tutorial-list/http://blog.oscarliang.net/how-to-choose-motor-and-propeller-for-quadcopter/