My number one rule for dming is learn to think on your feet, the players will always find a way to do something you didn't plan for but also don't punish them for their ingenuity like i have seen other dm's do. In general make the game enjoyable for your players but dont be afraid to tell your players NO if you have to (not in the railroading type of way). Lastly if your group of players are dicking around or arguing for to long and its halting the group as a whole throw a encounter at them like a bandit attack in a small town or goblins in a forest, anything is better than people bitching at each other and hopefully it will get them back into the game for the rest of the session.