Just put enough water to cover the cells...
FYI - if you bought ur battery from Automotive Components (Power Master) and you have the warranty card, just go into any of their outlets and let them check your battery for you. They do that for free (once its their battery of course) They usually advise every three months.
And if you have a battery
I'm not too sure about Laughlin & De Gannes though (they sell Rocket batteries), though I will find out... (cause I have a Rocket!)