This is not a "how to", as much as a, well..."how to?"
The major hurdle I have currently is that the players in my gaming group are long time (as in playing D&D since there was a basic and advanced D&D in 1980) hack and slashers and I am concerned that I am going to be unable to teach these old dogs any new tricks.
As anyone who has set foot on the Acolyte's path will tell you, the game often has more in common with a good film noir than an all-out, everything exploding all the time, action thriller. Yes, sometimes there is intense action, but due to the scale of the forces arrayed against our valiant quasi-heroes, they need to be well-informed and well-armed to survive to make it to gaming session 2.
By way of example, let's talk about a guy who is playing an ex-guardsman. Odd events have been happening, including strange psychic phenomena. When he begins to get the feeling of being watched, instead of thinking about things rationally and possibily alerting the ranking acolyte who happens to be a psyker (as his character bio suggests that a veteran of several campaigns might) , he goes buck wild and lays down a swath of laz-fire that is enough to take down a charging hive tyrant!
In short, the group is not interested in gathering clues, working the populace for information or following the trail to the source of any xeno or chaos activity. Rather, they would rather kill everything in the area (EVERY area), every game.
I am pretty sure that this group is a lost cause but on the off chance it's not, what would you try to get these people to understand the way the game is "supposed" to be played?