Like davidmc said, take stock of your group and have a think about what they're going to enjoy. Maybe ask them some questions if you're not sure. Some people like roleplaying to be heavy and character driven, others prefer things to be a bit more silly. Some people like lots of combat and dice rolling, others prefer to keep things as diceless as possible. The key thing is that everyone (including you) is having fun, so try and come up with a tone or balance of tones which is going to give everyone a bit of what they want.
Secondly, think about what your style is as a DM. For a very narrative game, you will be feeding the players a very clear path which they should follow in order to get to interesting encounters and situations which you've planned out. This works well if the players are less powerful than most NPCs in the setting (like vampire the masquerade) because the NPCs can always step in to keep them in line. Be sure not to take too much control away from the players, though, they will have their own reactions to things which won't necessarily align with your carefully crafted story, so you still need to be ready to improvise a bit.
For a more simulationist game, the players are much more proactive in leading the story, while you are the one reacting to their decisions and actions. There should still be an interesting story and you should have an idea in your head of how things would play out without the players interfering, but they're leading you not the other way around. This kind of game can require either a lot of planning or a lot of improvisation, as you're not so much writing a story as building a whole world with characters and locations and just letting the players run around in it. This kind of game also requires that the players be proactive and have strong motivations for their characters. A good idea is to sit down with the players when they generate characters and go over the basics of their motivation, backstory and why they are a party to make sure they are compatible and have something to do. When they work, though, these kind of games tend to be very memorable.
Or you could just aim for something in between.
I haven't played wraith in ages, but it has a lot of mechanisms which actually work in your favour as a DM. The game requires the characters to quantify their motivations to a degree, making it easy for you to play off them, and each has a built in antagonist.
