My first game... did not go so well. I ran the "Beneath a Metal Sky" adventure from the book, and, bolstered by the constant recommendations of this as a great gateway game/game for newbies, I ran it for a group of 6, only 2 of whom were experienced roleplayers.
I ran Metal Sky for the first time I did Dread as well. I had 5 experienced gamers playing it. For the most part it worked out well for me. Only 2 deaths and both were player sacrifices to save the party.
I did feel that it was a bit rail-roady on my part. As there was no map of the ship, I kind of just made up places where things were as suited me to setup the next attack.
In my view, it seems that the tower is really building up to the next attack when somebody will fall. If the players are active, doing smart or silly stuff, they will make pulls. You don't need to punish doing reckless stuff by having a monster attack right then. The consequence is built into the tower. When it gets rickety is when the big monster attack comes that kills somebody.
Conversely, if the party plays it safe and hunkers down, you need to instigate change and action. This invariably means the monsters attack their position and cause a failure in the defenses that forces them to move or rush to action.
I think with this paradigm, the GM should generally reward players taking action. The players who attempt to do stuff should see success or new situations develop. There's no need to nail them with monsters if they keep doing stuff (after all the tower will nail them eventually anyway). Lack of action is boring, so bringing in the monsters to force the players into action seems fair (and part of the genre).
In Metal Sky, this meant that players who explored, found gear, new exits, etc. Players who hunkered down, would get ambushed and attacked. This actually keeps both types of players busy and involved, just in different ways.