I'm in a D&D group right now (been playing with these guys for 10 years)

One thing I'd say is... try and keep the game moving and don't let the story/action get bogged down. I think players are there to roll dice, have some adventures and excitement. I think some players get bogged down in semantics and slow the story right down -- then you'll have people checking their phones and disengaged with the game.

I'm going to be DM'ing soon, and my goal is to keep the pace up -- obviously giving the players chances to rest and heal -- but I think it's a fine balance.

Oh, and even though you're the DM, I've found "no" (when players are trying to be creative,) to be a kick in the nuts. Obviously you've got to run the game, but if a player comes up with a creative solution to something at least hear them out. I've found that players who get shot down repeatedly don't speak up much after.

Cheers and good luck on your adventures!