Salutations,
I have found that the general environment of the gaming impacts a lot of it.
Before we played at my place, we played at a buddy's house- and used his couches in a room with tv and video games.
It got better once we moved it to my place- I have a room set aside for gaming, and everyone sits up and faces each other. The tv is also in another room.
It may also depend on the type of game your players want- if they are casual players, then they may just want to joke around and such.
The only other tip I can think of besides talking to them about it is trying to change up your sessions. Have on session be a tough dungeon crawl, the next a political-type rp'ng, another a run-around type. Try to keep track of whats gets your players involved the most- and try to work more of that into your adventures.
Good luck
SD