This is now i make all creatures (human or otherwise) for my games.
Find flavor: What does the creature do, does he have a ball and chain? or is he really quick ect...
Find a Role: Is he a striker ect..
Powers: Make up powers that fit the role, some kind of whirlwind attack, some ability that lets him use a more than once.
Stats: Check DM tool box for damage output, def, and + to attack ect. that works with the level of the monster
Balance: Look up another monster in the MM with the same level and role and check to see if the are about the same power level.
There we go, now it does not matter if it's human, dragon or Demon
*side note: i do look up racial abilities for that monster and check to see if i want them to have that ability (9\10 I do)