Two things that I enjoy to develop story . . .
-
Drop little little things in passing during sessions that at the time seem like throwaways only to be brought back down the road. Essentially foreshadowing, just not so blatant players will expect it. Example: the PCs find a file or letter in a referencing something unfamiliar. Is it just flavor or is it a piece of intel for a plot thread introduced multiple sessions later?
-
Make an effort to pay attention to PC backstory and/or their in game development as told by their player. Take notes if you have to. Then have the world (NPCs etc) specifically react to those things.
I’ve learned over time that as a general rule, GMs care a great deal of their overarching story or world, but the players are primarily invested in their characters. GMs may tend to overestimate the players’ investment in the world. So, in short, try to make the PCs the real stars. It seems obvious maybe, but worth reminding ourselves.
One way to accomplish these things is to work it into your adventure design. Many GMs have a “planning structure” such as Timers/Threats/Treat in ICRPG. In that vain, I try to make a conscience effort to plan one or two story notes or NPC reactions customized for one or more of the PC per session. These can be really small things but they tend to bring smiles to the table.
All of this is clearly easier to do for developed PCs in a campaign than in one shot. But it can be done in one shots as well .