j = 1;
A =   Table[
        Random[Real, {-1, 1}], {4}, {4}]
Vec  = 
      Abs[ A[[All, 
          j]]]
BigSpot = Position[Vec,  Max[Vec]][[1, 
        1]]
Temp =  
      A[[BigSpot]]
A[[BigSpot]] = 
        A[[
          j]];
A[[j]] = 
        Temp;
A