One challenge with GMing Dark Heresy is establishing the feel of the 40K-verse. After all, how GrimDark it is, is up to the GM- there are some large differences in the fluff between Rogue Trader compared to say Dan Abnett. But even with that, some elements of the Imperium are harder to convey to players than others -getting out of the idea of technological improvisation is one for example.
So heres some things I do -
In Hives, there is a daily "Thought for the Day" message- the speakers crackle, play the "Emperors March" and everyone comes to a halt in the streets and factorums, listening intently as one of the Thoughts for the Day are relayed to the populace - "Hate The Other" or "Questions are a Burden on the Soul of Humanity" . This serves to emphasise the fascistic aspect to the Imperium with its very definate propanda.
I mix 1930's tech and mediavael stuff with modern hi tech- when they wanted a spy camera the only thing they could find was an Victorian style photographic plate camera with the little shroud for the photographer to duck under and a tripod stand. This is whats being produced now- if they want a tiny, camera phone then they are looking at requisitioning a 2,000 year old artifact from the Adeptus Mechanicus. This helps emphasise that technology is degrading rather than getting better.
SJE