Describe the terrain they are passing through. Include a few interesting sights along the way. Don't be afraid to toss in a random non-adventure encounter, like the players passing a prey animal or seeing other travelers headed back to town.
And, this is most important, research the terrain they are traveling in. A forest is not just the trees, but also the shade, the scents, the animal sounds, the other undergrowth... Even a desert a has more to it than just sand.
I like the idea of rolling any wandering monsters in advance.
Ask yourself whether you need wandering monsters at all. From your comments about the vampire sub-plot it seems that you have some developed ideas already - I'd suggest choosing your encounters in a way that you think will push things in a direction you think is fun/interesting, and not rely on the outcomes of dice rolls to set your story and pacing.
And another perspective on narrating travel - I tend to gloss over it if nothing dramatic is happening. My players seem happy with that, and I don't think they are looking for me to give them descriptions of the shadow-dappled clearings in the forest, etc, unless there is something interesting going on in said clearing.
As a player, you never really know what is going to happen next. The secrets and the unknown raises the tension level. When you are a DM, you always know what is going to happen
Not quite my experience, because the players make choices that change things.
Relating this back to my comments about encounter planning - have your encounter ideas in your back pocket, but pull them out in a sequence and with a pacing that responds to the dynamics of the session as it unfolds. Provided you know what you've got, you don't need to decide in advance exactly how you're going to use it.
A simple example: you can decide on the pacing of combat-type threats by, in part, having regard to PC hp totals. If they breezed through the first wave of goblins, send more! If the first 3 goblins beat them to within inches of their lives, hold off.
A more complex example: if you've got your vampire idea, and the players pick up on it, then you can build it into other stuff you use later. Eg one of the goblins has a child's trinket around its neck. How did it get that? It must have got it from the vampire, who took it from the child's room. But why was the vampire trading trinkets with the goblins? You don't even need to work that out in advance - you can follow the players' leads.
when confronted with the child's injuries you probably want let the players know (through a party member's knowledge or an NPC) that the wound is likely from X creature, and that X creature is likely to do Y (Y being what you think is likely ie; coming back at night).
My own view would be to hold off on this sort of thing - rather, I would suggest letting the players draw their own inferences and make their own choices, and then (as GM) you can riff off those. This also feeds into the comment about tension and uncertainty - if you're following the players' leads (in your decisions about pacing, framing etc) then you don't know what's coming next either!
Of course, if the players ask what their PCs know about vampires (or whatever) then you can give them a INT/knowledge check, and if the succeed tell them something that they probably don't know from their own folkloric knowledge (eg that the vampire can climb walls; or that it can regenerate - though personally I might drop regen from a vampire that I'm statting up for a 1st level adventure).
