What do the dane warriors do to avoid grendel after the attacks start?

If we refer to the first part of "Beowulf" when we are first being told of Grendel's attacks, we can determine what the answer to this question is. We know that Grendel was jealous of Hrothgar's kingdom and the happiness they had since Grendel was an outcast, a son of Cain. He would never experience the happiness and joy that Hrothgar's kingdom had which is what made him start attacking them as the mead hall was finished. The only way for the men to escape certain death was for them to not sleep in the mead hall each night. Any man found in the mead hall after dark was guaranteed to be killed by Grendel and possibly pulled into his lair beneath the water.