Peter Molyneux, famous video game designer and hyperbolist, mentioned a kind of ‘trail of breadcrumbs’ when talking about Fable 2. The idea was that it would be a sprinkling of golden glitter which directed you ahead to your mission, so you wouldn’t focus too much on a minimap instead of the world itself.
It’s a little tricky trying to do the same with RPGs. I’ve run games so long I’ve been accused of being a railroad GM, but I’ve also run games with such an open sandbox that players sit around, unsure what they’re supposed to be doing.
I’m not 100% sure of the right level of visibility of the breadcrumbs for groups in general, although your players can often help. I had a real problem in my Tremulus campaign. The default setting is a small town and it suggests that players have characters who are fairly recently returned to the town, having originally been from there. We had one player who followed that remit, while the rest made basically vagrants. One was a hobo, another was a travelling conman who played at seances until he stumbled upon a real one, then the third was a gravedigger who lived in his van and did have a relative he was a bit distant to. The system gets you to generate a bunch of plot threads for local mysteries and then hopes the players will solve them.
The problem with this game came when the player who followed the remit left the group. Everyone else was wondering why they stayed in the town and why they didn’t just leave. The worst thing was they were right. They didn’t have any motivation to stick around. I called in a ringer as a player, who I briefed on my problem. He made a local boy who’d left and come back to play politician. Getting that buy in just from one player was fantastic. It meant he could pull the others in as people who weren’t really known or accountable. He was tied into the mystery, as was the aunt of the gravedigger.
It’s a tricky thing to do right. I love bringing players in to help, but that’s only one way of helping try to lay out the threads seamlessly. Personally I’d love to hear what other people have done with their plot threads to keep players following the breadcrumbs.