A friend of mine actually has quest logs.

So as soon as the party finds a quest (= pointer to the plot), or they make one up on the fly, they write the quest on an index card* and hand it to the players, just like you might have a quest log in a computer RPG. Find the location of the Eyrie, Recover the diamonds from the mountain lair, and so on.

I seem to recall also doing this myself in 4e back in the day, but I can't remember if that was something the system recommended or something I improvised. I think the former.

If the party have a stack of cards with quests written on, they can refer to them and choose which one to follow.

They might not want to follow the quests, preferring to plough their own furrow. But as long as you and they are having fun with that, that's fine too.

*technically they use http://almanac.wiki instead of actual index cards, but the method's the same

You're not being as obvious as you think you are

Something that is obvious from your side of the GM screen is not necessarily so from the other side for all sorts of reasons. I refer you to atenção seletiva Por exemplo.

The three clue rule

You have to give your players finalmente 3 clues if you want them to follow a lead because they will overlook one, misinterpret the second and talvez work things out on the third.

Forget the story

Just set up a bunch of loosely connected adventures and let the players kill stuff. You can then say "The adventure is here."

Railroad them

Railroads are only a problem when they are a problem - if your players are happy being led around by the nose lead them around by the nose.

Find different players

Some players do not care about the story and never will. If that bothers you find players who do care.

Move incentives around and add mechanics around the thing you want players to interact with.

By default, 5e has piles of combat mechanics. If a player wants to swing a sword at something, by golly, 5e will tell you what happens.

It has next to no quest/adventure mechanics. And basically zero of it is player facing; the DM can hand out quest XP at some point, but a player is reduced to finding story hints and hoping the DM hands out said XP.

This gives a really long reward cycle that can fail to encourage players to focus on it. Meanwhile, combat has a multiple reinforcing reward cycles -- the player is narrating story right away, each round gives a bit of spotlight and a set of things to do, the combat is done after a few minutes and you get XP and have defeated the foes, etc.

There are many sets of house rules out there that can bring "find and do quests" into the mechanical hands of the players.

Aqui está um (not mine).

Here is a thread talking about it, more specifically talking about bringing story-based game fail-forward mechanics to 5e, with a lot of "get the players mechanical hooks on story" discussion within, including actual play experience results.

The basic bit of the idea is that you replace the default 5e XP system with one that is based mainly around resolving quests and resolving BIFTs (the inspirtation mechanic in 5e).

During a session you can earn XP by spending inspiration or failing a roll that matters (like, missing every attack in an important fight, or a skill check that has serious impact on the story).

Each session, a player can earn an XP by resolving and changing a BIFT based off the story.

Each session, the party can earn a single XP by gaining a treasure, defeating a difficult foe (EL minus Party Level XP), making a powerful enemy who remains at large, discovering a significant fact, forming a significant alliance. Each of these can only be earned once per session.

Finally, each player can crio a quest or mission at any time. At the end of each session, each player adds a point to a quest or mission they have. When you resolve the quest or mission, you gain that much XP at the end of session. So if you resolve a quest/mission in the same session you create it, 0 XP.

What is going on here is that we are structuring the XP system to reward a certain kind of play. Second, we are giving players agency to craft their próprio quests/missions, and giving them physical tokens to remind them of that quest/mission.

Instead of rewarding them at the final of a quest that you provided, you have players in effect rewarding themselves for finding a quest/mission almost immediately (with the card), then over time (investing points into it), and finally when resolving it.

Throw fewer monsters and more non-combat challenges at them.

Sure, with enough ingenuity, players might try to brute force their way through, for instance, the castle gates by killing the guards, but if they were to do so, they'd probably get a hefty bounty on their heads and the king wouldn't dare talk to them. Anyway, I digress.

D&D has a lot of mechanics for out-of-combat interaction, which is where the story is. If you end up spending the overwhelming majority of your time killing things (especially since an encounter usually takes at least 20 minutes), it's no wonder your players will lose track of the story.

Intertwine combat with the surrounding world. I think we often, as DMs, compartmentalize combat and story, but if you take the approach that the bandits have lives outside of thievery and make real and lasting consequences for what happens in combat (e.g. bounties, people avenging their wanton murder, callbacks to previous battles, etc...), players might put some more thought into the world and its story. Combat is an interaction and has just as much potential for story as anything else.

It's also possible that you have the type of players who just like combat and killing things. You might be better off finding players who are more interested in story and less interested in combat.

Reward quest completion with additional XP.

Like piersb said, using "quest cards" can be helpful to remind them of their goals, but if your players are much like mine, they will be mostly interested in the "next level", and less about the greater good. You can implement an XP bonus for completing quests that prompts the players to prioritize completing those over killing everything in their way. Following the story is a big incentive with this system.

To help your players discover the plot hooks, you could give the quest cards for discussing the right aspect of the hook, like a letter or a trinket. For example, if they find a letter from a farmer's son in his abandoned cabin, asking each other and you about the bandits attacking the son's village could trigger a quest to convince the powerful bandits to leave.

Finally, for the system to work, you need to explicitly state that the players will gain y XP for completing x quest. Also, make sure to remind them of their current quest cards at the beginning of every session, so they know what their priorities are.

Lure them to the quest by the things they are interested in. If what they want are to flex their muscles and have a good fight, have a super easy encounter (small raid party) where they are, to let them know that a good fight or loot awaits them at location X, where you want them to be for other reasons.