What is the plan of attack? How many vikings are fighting/raiding with me? What are we armed with? Who is in charge of me? Where do we go to find the "booty"? How did we pick this particular site to pillage?
Not discouraging other answers here, but you can get started with these posts
How good were the Vikings when it came to fighting? and follow-up here In the show "Vikings" (2013-), the vikings shown fight in a style very similar to what seems to be a Greek phalanx. Is this accurate to how Vikings at the time fought? And is there somehow a direct connection to Greece where they would have learned the style?
What tactics did viking raid victims come up with to counter the invasions?
How effective were fortified bridges at preventing inland Viking raids in early-medieval Europe?
What kinds of people did the Vikings take for slaves/thralls?
Can the traditional "campaigning season" be applied to Viking raids?