1. bravery - obviously the hero had to be brave if he wanted to defeat the monster. I believe that the Anglo-Saxons valued bravery and strength because they themselves were such people
2. loyalty - Beowulf is loyal to his king and came to his aid to protect his people. It was important for Anglo-Saxons too to be loyal to their leader
3. being a good person overall - if Beowulf wasn't a good person, then God wouldn't have helped him defeat the monster