Quote by Van
Same here I stumpled upon two of them, one while doing the first set of heroics on the home planet and then one in the under city.
The one on the started planet was way out of the way on top of some mt that I would have never thought to go to. I just saw something glowing and had to go investigate. The one in the under city was right out in the open.
Some are incredibly easy and yet incredibly fun at the same time. One in Coruscant requires you to drop onto a ledge, run around to an abandoned taxi and then (it) drive(s itself) to a little gondola beneath the main taxi platform where you get a Datacron. :)
Some require you to go completely out of the area and then "ledge" hop back.
On Tatooine there is one that, again, you have to drop onto a little ledge and then go through a cave that is lousy with sand people (although some people cheat and lure them to the ledge and use a knockback power to get rid of them) and you end up coming out of a cave mouth above the original level you left.
Not even a keen eye will show you the way, sometimes.