One trick for all greater monsters is to make them characters rather than objects. It isn't a dragon. It's Gorafzasdzatraxxes the Fearsome, destroyer of fourteen villages. Vanquisher of the giant-fortress of Magna. The green beast. That gash over his milky white eye? He got it from the axe of the king of the giants. The scar across his belly from the dragonslayer Sir Ramshood.
Dragons are certainly few enough to be easily recogniceable (and vain enough to ensure that they will be) and if you know enough about dragons to recognice what this "type" of dragon is capable of, then you can probably identify which one it is too.
Unless it is too young to have a reputation, but then it'd probably let the players know to build just that.

Trick two is to ensure that they always have a reason for what they're doing, and not just show up to provide a challange. Gor, above, for instance, might be building his hoard and engaging in dangerous fights to build up a reputation in order to impress his fellow female drakes. Proving he's more than a capable mate that will grant her good strong spawn. And he's ravaging the countryside to make sure they know where to find him (and to eat, of course).

Trick three is to ensure that everything fights as they should. Dragons are intelligent (if alien) and wouldn't deign to fight fair. It's lair is full of maze-like passages and 9 m shafts straight up or down. They're long quadpedal species with strong claws, it's not an obstacle to them. Long underwater passages that a dragon easily can hold it's breath in, but is quite too long for a human. Sure, it'll probably take forever to build... but dragons live long.

In open spaces they'll do flyby's, not landing anywhere without clearing the area with spells or their breath first. ensuring that not a single one of those little things with sharp sticks get close to the soft underbelly. Dropping a massive treetrunk on the wizard. Causing an avalance (if in snow-covered mountains). Scaring a massive herd of cows/wildebeasts towards the PCs.
Making frequent use of illusions to hide the truth of things. Tipping over the boat they're on.