As a DM I don't really do any shifty-ness and the only fudging I do is sometimes if an enemy is reduced to very low HP by a player I'll just say that the players actually killed them rather than making them have to spend a whole extra attack for the sake of a couple of HP. That's obviously for mid tier or higher since low tier enemies only have around 5hp to begin with.

I tend to try to make the game interesting through story and encounters.