One of the things that I've always appreciated in the Dark Heresy game I am in, or in other games by the same GM, is what happens when a big turning point is coming up in the plot. You know the moments, right? Where something - usually that would be out of the PC's direct control - is coming up and it could vastly change how things play out. The big things that can steer the course of the entire story. Yeah, those. I want to talk about them today.
The Players Deserve A Say
The first thing you need to understand, especially for what comes next to be understood, is that the players deserve a say in where the story goes. Why? Because they are just as involved in the tale as you are. If the PCs don't want to deal with yet another Arch-Magus trying to summon a greater demon, then maybe you shouldn't do that. By the same token if the mission could either send the PCs out into the forests of shadows or the caves of death, and half the group really wants to explore that forest...don't you think they should get that chance?
RPGs are cooperative story telling games. That doesn't mean everyone always agrees, but it also doesn't mean that the GM should be the sole person deciding what huge swings the plot may take over the course of the adventure.
The PCs are the Protagonists
The other thing to keep in mind is that the PCs are the protagonists for the story. This means that, at times, they should have a greater leeway to make decisions. They're more likely to be left in charge, or given a shot in a key position, despite being new to a group. Why? Because, quite simply, they're special.
Look at the various movies, tv shows, comics, and books you have. In all of those the main character is given the ability to make big decisions because a protagonist without a sense of agency isn't much of a protagonist. Your PCs deserve the same choice.
When the PCs Don't Have A Say
Put these together, and it is still worth it to give some choice to the players even when their characters wouldn't have a say. For example, in my last Deathwatch session there was a chance that the PCs could be going to explore some underground tunnels - where they'd have to go against the denizens of Chaos - or explore a space hulk - against tyranids - and the decision hinged on whether or not the Grey Knights were available and close by. Now, there were two ways I could have done this. I could have just rolled - or arbitrarily decided - if the Grey Knights were available, or I could give the players the choice.
I gave the players the choice. Why? Because it is their story/game as much as mine, and I wanted to give my players what they wanted to see in the game. They put it to a vote, and decided to go for the tunnels. Everyone is very excited about the mission though - including me - and some of that is because this was a course that they chose for themselves. Part of it was also because..
Let The Players Tell You
After they made the choice, I asked the players to write down what they wanted to do, and what they wanted to see in those tunnels. Now, some of the things they want are flat out - and they know this is possible - because of story elements already in place. However, other things are able to be worked in. These things include personal plot hooks, and just encounters that the players want. This inclusion in the decision making process has made my job as a GM remarkably easier, and has people looking forward to seeing how things play out. Win/Win.
Do you do this? Have you tried it? Did it work? Anything to add to this? If you have never tried it, I highly recommend giving your players some more say in what happens in the game. It can work out amazingly well.