I need to operate two high torque servo motors : HITEC HSR 5995TG using single battery pack.
Also I need to drive two low torque motors : HITEC HS322-HD using another battery pack.

plz help me find the suitable battery pack.

What exactly should I look for in selecting a battery for driving servos?

any 5 cell NIMH pack

6 volts

i personally like this one

http://www.teamtrinity.com/shop/item.asp?item=TRI20508

what type of vehicle?

i like the IB 1400 5 cell packs...i run Hi Tech TG servos in all my rc's and the IB cells work great for me, have ran many 45 minute mains with them...