Always make sure to place the griddle on level grates. If one grate is larger than the other, make sure to set the large grate's flame to low and the small grate's flame to medium or high so that the heat distribution is even and one side is not colder. This is what causes griddles to warp, bend, or buckle.
Never submerge a hot griddle in cold water; always allow the griddle to cool completely before washing or wetting it.