I recently started running Hoard of the Dragon Queen as a DM and this is the first time for me. During the campaign there are a lot of journeys that take several days, even weeks, and in some cases nothing important happens. Now, my question is: how much time should I dedicate to them? Should I just say "You travel from A to B in X days", maybe adding some details about the road, or should I provide a longer and more detailed description? The same question holds when some important events are planned: should I move directly from one event to the other, like "two days after event A, event B occurs"? I read the advices in the DMG but I would like to have more specific indications on the typical approach. Also, I am afraid that if I start describing some elements of the environment (a waterfall, a big rock, a tree and so on) then the players start investigating about it thinking that it is important for the plot.
So you only have enough time for either finishing off the adventure, or dealing with random encounters, but not both. Therefore any solution requires spending very little time.
One acceptable way to handle it seems to be to narrate it away. It's entirely legitimate to narrate their travel through the wilderness and cut to the chase, so to speak. Your players won't object, and are even likely to be thankful that you responsibly paced the session so that it had a natural and enjoyable end.
I wouldn't bother with any resolution mechanic, even a simplified one. Sometimes travel in the wilderness is uneventful. Take advantage of that, plus your power as the controller of the world and your responsibility to pace the game well, to just make this time one of those uneventful travels.
If you feel that it is really unrealistic for this trip to be uneventful, mention what trouble they encounter along the way in the past tense, off-handedly, and conveying that "of course" they handled it without any difficulty. For example, encountering and quickly dispatching an already-weakened patrol of orcs can be glossed over in a sentence, giving them your acknowledgement that the PCs are kick-ass and that was nothing to deal with. Lead right into a description that places them about to engage in the final action of the session and you're good. In systems where encounters lead to XP of some kind, I wouldn't hesitate to give them a token amount – unless the resistance was really beneath them.
Roll For Complications
You don't want to take any time dealing with the travel, but that doesn't mean it has to be meaningless. Taking a page out of Dungeon World, you can call for a roll to test something during the "perilous journey". Decide on a possible complication of the journey that might lead to a mild consequence for them to deal with at their destination.
Perhaps you have them check if they move stealthily, and when they arrive the inhabitants have been warned of the approach of armed people, or not. Perhaps they make a survival check to determine whether they arrive hungry. Perhaps their pack animals were spooked at some point, and an animal handling roll will determine whether they're down one donkey and low on torches and lamp oil as a result.
Whatever complication you think will be interesting, present the potential event, describe the possible consequence, and call for a single test of their abilities to do well. If you like, you can come up with two or three (quickly), and give the players a choice about which one they want to risk on a die roll (they get success on the others free). This is a very quick and flavourful way of making the travel meaningful while concentrating their attention on the important thing: the final action of the adventure.
So it sounds like you want to add some thought, memorability and danger into the travel time, but you don't want them to meta-game things so that they are overpowered by the time they reach their destination. You don't want them 'hanging around' these locales longer than necessary, over-foresting the fiendish-squirrels to extinction for XP. I would handle this a couple of ways:
Low treasure for random encounters
If you award XP by the book, with no extra 'story point awards' and keep treasure low to Nil (sorry the Dire Lions did not drop 100gp and a pair of bracers +4), I don't think they'll stay there long or advance too quickly.
Keep the CR level of the encounters in the Yellow Zone
I would keep it maybe at or a tick or two 2 above the party level; whether from sheer numbers of opponents (a large # of giant ant warriors) or quality (1 hill giant) or circumstance (see weather below). I think that most wilderness encounters are things that players should at least think about avoiding or fleeing from. These are encounters that should bloody them if they take them head on.
Roll encounters 'randomly' in advance
Roll a few (2 or 3) wilderness encounters in advance and write the results down on notecards so you at least have some idea of what they are going to be ahead of time. Helps to think about 'if this goes down, here's how it will go down'. Then for the encounter check, you are rolling to see if the encounter occurs (not IF it occurs and WHAT it is; you already know what the WHAT will be. You can also determine the encounter distance in advance or things like that)
Roll the Weather in advance
If there is going to be a lot of overland travel time expected, actually roll the weather up for the next three months. This (can) add a lot of flavor to encounters that do happen. Fighting a Troll in the middle of rainy deluge (or even a dry spell where the whole forest is ready to go up like a matchbox) can be a whole different ballgame from what players are used to. A swarm of Gibberlings in dense fog banks could also be unnerving; it is the Wilderness, so play up the different conditions that can happen there.
Track player supplies, and make foraging a dangerous challenge
In many of the classic fantasy novels, starving or dying of thirst is a real problem. This gets overlooked too often I think, or just 'handled' by someone making a Survival check at +10 or the like. Set some higher DC levels for different areas for foraging. When foraging, check for random encounters. (you might not be the only predator tracking that wild boar...) If an area has a low forage yield, it may be inhospitable, or there may be a real 'top of the line' predator around causing the imbalance.
Use Stalking encounters
Quite a few monsters (natural and unnatural) tend to stalk their prey for quite some time and 'wear them down' preventing them from resting, picking off stragglers. Wolf packs, Meenlocks and many others might come to mind here. Being in the wilderness means there is no safety. You may know 'something' is out there, you might even skirmish it into a quick retreat, but that doesn't mean it isn't going to come back a little later. Stalking is probably waaay underutilized in the wilderness.
Make it a challenge for the characters to exist in the Wild, and they'll not only remember it, they may feel relieved to get to where they are going.