There are more ways than one to encounter a dragon. With a low level group it's obviously not feasible to meet one in its lair and fight it. But standing on a bleak moorland, utterly exposed and vulnerable, it can be a chilling experience to see something flying far far overhead. Something that could just be an eagle, but you never know...
The PCs are setting up camp at the end of their first day of walking through the Esh-Inel Mountains, when they hear in the distance a low rumbling, like thunder. It grows progressively louder until it echoes off the mountainous bowls around them, then dies away again. At its worst the ground starts trembling. It happens every day at this time, and it is the noise of the Great Carts on the dwarfish underways returning home after a day mining, laden with many tons of ore.
The ochre sands stretch for miles around. Something kicks up the dust. It's a yak. A desert-yak. It ambles slowly, nuzzling the ground for the low-growing shrubs. The ranger freezes. "Stay very still," he warns. "Don't move at all."
"What is it?" you ask, breathlessly.
"It's the most dangerous creature in the whole Ocadian desert. And it's about to eat that yak..."