Pacing through scenes and transitions

Pacing is probably one of the most important aspects of storytelling.

You have to manage the time and effort you are spending on the different parts of the story.
You have to distinguish between "scenes" and "transitions".
A scene is where something interesting or important will be happening, where players will be finding clues, will meet one of the important npc's, will be dragged into a fight, will be advancing the plot or any other scene that is somehow actively involving the players. Remember they are not sitting around your table just to listen to your story.

A transition is the part between two scenes, like travelling from one place to the other, the days the characters spend resting, researching or celebrating etc. or any other trivial matter that will be going on during the story.
The transitions should be kept short. You can narrate it in one or two sentences, just to set the mood.
Example:
"After a short ride on the overcrowded subway and a long walk through the never ending rain you finally arrive at your Sire's villa."
This is always preferable than asking your players how they want to travel there, when they will leave, explaining them what they see on the way there and describing them the subway train in every possible detail. Save your energy for when the interesting parts come up.
It's during the scenes, where the interesting stuff is happening, that you should put a lot of effort in describing what they see, hear, smell and maybe even feel. Here you should take your time to set the mood for the scene and hand the acting over to the players again.

Some groups or players will actually enjoy to be able to roleplay their character during a downtime of a story, even if it doesn't relate to the plot. If that is the case, and they are asking for it, by all means let them play trough it. But you shouldn't be forcing this upon your players.

So it all comes down to highlighting the scenes of a story, putting weight on those parts, taking your time to describe, set the mood and play them trough, all while keeping the transitions short. Your story will advance  much faster and you will have less trouble keeping your players interested and attentive .
Think of it like a movie. If the movie is showing unrelated trivial stuff between the scenes, you will most probably be bored. And so will your players.

This has of course to be taken with a grain of salt. Nothing keeps you from describing a location beforehand, as an introduction for stuff that will be happening later on. Like handing out a map of the ship on which the characters will be spending the next month. Having them settle in and explore, and have stuff happen later on.
If on the other hand they just use the ship to travel from one place to the other, you can save yourself the trouble and skip to where you wanted to take them.