When running a tabletop role-playing game campaign, we want to draw people in. We want to hook them and have them looking forward to the next session. And as is the pattern for this kind of thing, it isn't easy. Different people may need different things to draw them in. Though I of course cannot offer a definitive opinion or an exhaustive list, I hope I can offer a few helpful tips at the very least.
Types of Games
The nature of the games we're playing has a large impact on the kind of things we can use to hook people and how important they are. In a one shot, doing so quickly and efficiently is very important. We have very little time to work with so we need to make use of it effectively. In more relaxed settings, such as a long home campaign, we have a bit more time to work with. However, getting players interested in the goings on is still extremely important. It's just we can be more subtle and measured instead of being forced throw our players right into the thick of it.
Hooking vs. Maintaining
Hooking, grabbing the interest of players at the start, is different than maintaining interest. Of course, both are important but I want to focus just on the hook for now. It also wouldn't say one is easier than other, and there are many overlaps. However, they often work in different ways.
Start With Actions
One of the easiest, most straight forward and effective ways I've come across is to make sure things start with some sort of actions or events. It's similar to the idea of show, don't tell. Particularly when you don't have a lot of time to work with, the adventure might need to come to the players. Of course, the players still need to make the choice to go on the adventure.
What do I mean by actions? Let's take the classic situation of all the players being in an inn and meeting each other. This kind of thing is more of a setting for an adventure and not an event. If we now had the inn catching on fire, attacked by someone or have an injured stranger collapse into the room, we've got an event that can capture the interests of players. These kinds of events, from my experience, tend to work best when they hint at something bigger. They are parts of stories, and that's a source of their power. However, they should also be able to stand alone and be interesting on their own. In a long campaign your first session may be aimed with the expressed goal to try and hook your players as well as introduce them to your world. In this case, it should probably still be part of a larger story, but also function as a story on its own.
Keeping this kind of thing in mind is a good idea in general. Instead of hearing about some event, you can instead show the consequences of the event. As an example, show the large influx of people as a result of armed conflict to the north instead of just hearing people discussing it in the bar. You can still keep the discussion, especially since not all details will be immediately noticed. That's fine though. After hearing the conversation there can be that “aha!” moment.
Also don't be upset if they don't bite at first, or go in a different direction. They may be waiting for more details before jumping in, or have great ideas you never thought of. I also find it helps to think of this as setting the stage. We'll set events into motion, and the players mess it up, twist it, and turn it towards their outcomes. Don't forget it's a shared story.
People often have their own pet themes that they love to see. I know I am guilty of it. If you know some of the themes your players find interesting, incorporating some of them is often an easy way to increase interest. Of course the execution matters too. But there are certain things that just resonate better with us. It might be time travel, or it might be the nature of undeath, but regardless it still helps. I've made my opinion on the matter of themes extremely clear. Having an overarching theme or themes helps in other ways too. It allows players to have a vague idea of the kinds of things they'll experience, without telling them what to expect. If your players are speculating about things that might happen or planning for the next session, you know you hooked their interest.
Combat, is of course, an event. It can also be a great way to get generate interest at the start of a campaign. However, there are a few things that I think need to be kept in mind. Even when doing so, the role-play considerations should be kept in mind. One of the great things about interesting combat encounters is that they have real risk and force players to weigh options. However, once over, they can often be forgotten and fade into the back ground. Having the combat encounter be an event that relates and pushes the story forward means that it is not so easily forgotten. Instead, it keeps generating interest because it still has a link with the future. Fighting random wolves in the forest doesn't do this, unless of course it turns out that the reason that the wolves are forced out of the forest is an army of undead moving ever closer.
Even if there is a reason in the background for it, your players need to know or at least have a suspicion or it won't work. Instead you'll have a revelation moment, no speculation, and no real payoff. I want my players to feel something is off and want to discover what that something is. Another thing to keep in mind is the general skill level of your players. Throwing players right into combat can be daunting for a new player. However, when planned properly, it can also be a good way to introduce them to the combat rules. It also helps establish the kind of game they will be playing. Will the battles be big and grandiose, forcing the players to use all of their skills and abilities? Will it be a longer battle of attrition where one battle won't kill them, but using the wrong resources at the wrong time will? Or is it your special blend of both? A well designed combat encounter can be talked about years later.