Most adventures focus on Plot (what has been done or is being done), Conflict (triumphing over adversities using dice and mechanics), Character (how people feel and who they are), or Setting (immersing people in a sense of place). Any good adventure has all four but naturally some play styles and adventures prioritise them differently. Some campaigns very strictly prioritise one over the other. It can help to think about your priority list for these four things and to speak to your players about their own interests and expectations. Each of these four elements have their needs and their focus. Since a game only has so much time, you need to think about what you will prioritise during that time.
If characters are a big deal then there should be time available to build relationships, to explore a crisis of faith, to come to terms with changes, connect with the character's history through NPC meetings, among other things. If this is the least priority than players need to pack any character development into the moments in between major situations. It needs to grow organically from comments made at crime scenes and choices made during conflicts. Since there's no real time for it, it will likely occur more slowly through a series of progressive and minor details, if it occurs at all. NPCs all need to have a place in the plot or be relegated to mere tools. There's no use in the players giving their characters any children and expecting them to be anything more than a talking point. Any aunties or family friends need to either be plot points or useful tools to the character so they should be described to the Storyteller in terms of occupations, skills and hobbies, rather than in terms of relationships. In a game like the World of Darkness, such fellows would need to be represented by allies, contacts or retainers if they're to come up at all.
If setting is a big deal then there needs to be time spent on cultural events and behaviours, historical detail, and physical descriptions of people and places. The players need to be aware that some time will be spent on where they are as much as on what they are doing there. They also should be given the chance to develop their character's background as they learn more about the setting so that they can adapt their characters to it in order to better integrate themselves into this reality. If it's a low priority then location descriptions should be short, sharp and snappy - perhaps with only one or two telling details on top of the practical necessities of room description. History and detailed cultural descriptions aren't necessary and will only slow the game down. Historical accuracy is generally not a big deal when setting isn't, though sometimes people want accuracy but just don't want much focus on the details of the world at large. Generally games which put setting at a low priority are better off with either generic settings or places which are
If plot is a big deal then there needs to be more acceptance that player's choices will be curtailed somewhat or at least limited in scope. This is necessary because heavily plotted games (like crime scene investigations) requires so much focused pre-session work involving locations of clues, prop creation, and consideration of situations that running off the rails or rejecting an adventure out of hand is a sure fire way to run into empty space with nothing to do and nowhere to go. Naturally even heavily plotted games should not be on rails. The Storyteller should think of the plotted adventure as a building filled with corridors, vents and doorways between rooms. While the players shouldn't leave the premises (thus departing the scenario), nor should the Storyteller provide only one path. If plot is a low priority, such as with pure sandbox games, then the players need to take far more responsibility in determining where they go and what to do. The lack of plotted spots set in stone (or even clay) means that the players may have little to no guide rails aiding them in finding their way through to their desired accomplishment. Such games are most often focused on the resolution of goals rather than the experience of rising tension through clear-cut beginnings, middles, and ends (though sometimes they may naturally form).
If conflict is a big deal then there should be plenty of creatures to encounter and obstacles to overcome. There also needs to be a clear-cut motivation and, ideally, guilt-free consequences for pummeling or killing dozens of minions to reach the conclusion. If there are to be high consequences of failure or discovery, or ambiguous enemies and villains, the Storyteller should be upfront with the players and be aware that the players might then choose to deal with some of these conflicts in a far less lethal and action-oriented way. If it's a low priority then there should be fewer opportunities for combat (as they take up a lot of time) and what combats and obstacles there are should be dealt with in a brief fashion. There also should be a variety of non-physical methods allowed in-game as the players might consider using their resources or social skills to defuse a problem.
Of course how much you prioritise each session is up to you but it's a good idea to keep some consistency through the campaign. After all, it can lead to confusion if a pure sandbox narrows several times into tightly focused plots and players can get frustrated at sudden interruptions of long periods of Conflict-Plot-Setting which broadens out into sessions focused on Character Development. Sure, you can pull it off, but it does make it a little harder.