This really is an important topic, not just because it can break your battery, but also because it can affect the way your atty works. I use Stardust clearos and I have had ones that just stopped working. I thought the atty was dead, but by tightening the connection to the battery slightly or loosening slightly, or loosening or tightening the drip tip, they have worked again. On Stardusts, the drip tip sits right on top of the atty head, so sometimes it can come loose when the tip has been unscrewed to refill.
I also tighten until just snug.