While this advice often applies to players, it is important to remember that as the GM it may also fall to you. Now, when I say a reason to be there for the GM I don't mean you need to figure out how and why the players go and do things. However, you do need to figure out a way for the players to get involved. This is often called the adventure's hook, and it can be anything from the promise of treasure, fame, and fortune, to something more personal. The smart GM varies the hooks they use, and today I want to talk about some of those hooks.
The classic hook for an RPG adventure is the one that starts with the players in a tavern before receiving the call to adventure. This call varies, but taverns are used frequently because they provide a reliable venue for overhearing things being said, as well as a place where gossip gathers. In this version the lure is usually the promise of riches. Someone hires the party, or they over hear people talking about some grand adventure and all the treasure inside.
The classic hook plays to adventuring as a job. The promise of a big score, or money enough to make a difference in the players lives. Sometimes it also plays to the desire for fame that goes along with the fortune. Titles like heroes of the realm, land, castles, a spot in the king's court. Either way, the hook here is simple: do job, get lots of pay.
I tend to call this the Fantasy Novel approach. With this hook the call isn't to fame and fortune, but rather the fate of the world. The need is so great that the adventurers have no choice but to head out and take on the task at hand, or the entire world could die. Sometimes it's not the world. Sometimes it is just the town, the kingdom, or even the local bar. The idea is the same either way though, need trumps greed and so the players head out.
Now even with this hook the player's motivations may be different. The players may wish to be heroes. They may want the fame and recognition from saving the world. They may see it as a great financial opportunity. That is up to them. The point is, as far as the world is concerned need is the main hook and the player's personal inclinations to it are up to them.
The Personal Touch
The personal touch is a great way to make an adventure, or part of an adventure, that highlights some part of who a character is. Sometimes these can seem a little convoluted or coincidental. I mean, are we really supposed to believe that someone from the rogue's past finds him and needs help just as he gets into a town? Seems a bit far fetched, right? Well, except that sometimes that i s what the story needs. Provided you don't over use this hook it should work out fine, and you can always tweak things to make it more believable.
One of the big bad's lieutenants - or the big bad herself - is someone from one of the PC's pasts? All the more reason for someone to hire the PC to go after their old friend, right? I mean, that personal connection could give them an edge.
The Revenge Job
Finally, you have the reason that can be among the hardest to pull off in a game on the big scale, but when you do - oh boy. With this, the PCs are out for revenge. Someone has taken something from them, hurt someone they care about, or otherwise just crossed one line too many. Now the PCs are going out after them and come hell or high water they're getting the job done.
The fun part about this one is that it reverses the roles in a lot of ways. The players become more active. The GM more reactive. It means you get to let the players put their plans in motion and work around them in a more dynamic way. Sure, you may have adventures planned for how they're going to hit this aspect or that, but for the most part this puts the PCs in a much more controlling position, and that can be awesome.