Next on the agenda we have...
How can the Gamemaster make the stakes of the situation at hand or even the overall 'meta-plot' important to the campaign, the PCs, and the players?
Relate it the PCs. Make it personal.
When developing my own campaigns I often have one or more overarching campaigns plots and ideas and numerous subplots or 'B-plots' in television lingo. What they all have in common is that they relate, directly or indirectly, to one or more of the PCs.
In the case of the primary A-plot, the story will have something to do with all the PCs.
In order to achieve this, I take the backgrounds, goals, and preferences of the PCs into account when developing my game. Although I may start with a campaign concept, I really don't create too much material until I know who and what the PCs will be. Once I have the PCs, I look for points in their personal stories or histories where the characters might converge or where something one of them did has similarities to something another experienced.
The best example I have in recent memory was our Traveller campaign, Operation: PALADIN.
Each player has rolled up a character and fleshed out their backgrounds based on the rolls they made. Each seemed very different and their stories unrelated except for all having taken place in Spica Sector, in or around the same subsector.
Until...hmmm...Kael battled a hostile alien fleet before his vessel was destroyed. What alien species? Hold on...aliens invaded the Mining Colony Dr. Fujikawa was on while he was in the Scout Service. The Ithklur are near that area working for the Hive Federation. OK. When I need a hostile alien for the campaign it'll largely be the Ithklur. When they show up during the campaign the conflict now takes on a more personal meaning to many of the PCs and their players.
"The Ithklur? Why those cold, unfeeling brutes! I owe them couple rounds of Gauss Pistol fire for...huh? You guys despise them too? Why? What did they do to you? Whoah. Really? OK, let's give them some much needed payback!"
It isn't just enemies either. One Player Character discovers her NPC son is Psionic in a society that loathes and fears Psi powers. Another PC is Psionic himself, and while the two PCs don't generally get along, the son likes his fellow Mentalist and a new relationship dynamic is formed. Meanwhile they need to keep in on the down low a bit from a third PC who, like an traditional, blue collar citizen of the Imperium, dislikes Psionics.
Make your players care by making the campaign their story.
It might be about many things but mostly, it's about them.