alright mate, i had a similar problem as our ls rarely gets used.
basically, u can buy a battery recharger. i borrowed a neighbours and it indicated 2 me that the battery was badly drained, recharged it and car is perfect, however, if you have a secure location that you park it in, e.g garage,it would be a good idea to leave the car unlocked, and about the use of that car i would say you should take it out every week or so on a long run, as this fully recharges the battery, whereas short runs can damage it further.
hope this helps,
Anuj