A SWTOR Datacron guide is not what you think. Well, maybe not entirely. The term "guide" in the gaming industry means that you will be guided towards a specific goal. Well with a Datacron guide for Star Wars: The Old Republic it isn't really so.
First of all, Datacrons in SWTOR are relics that grant the player a permanent bonus to a specific attribute. There are a minimum of three and a maximum of five on each planet. The bonuses granted can be +2, +3 or +4, depending on which planet you are on. You can also find some that give you a special item instead of an attribute.
The main problem with these is not that players can't find them. The problem is that they can't reach them because they are always set in all sorts of weird places. And that is why you need a guide.
It is pretty hard not to see a Datacron location because they are signaled. You will see a colored light shooting upwards from their locations. Not only that, but their locations do not change. So it is enough to ask a higher level player where he found his. But once you reach the location of the Datacron, you will see that it is up on a hill, or down in a ravine.
In order to get to them, you will have to go around hills and find hidden pathways and elevators in order to get to them. Without guidance, you can circle around a hill for hours and still won't be able to get to it.
A good example for this is a yellow Datacron on Dromund Kaas. It is placed on a rock that you cannot get on normally. There is a hill next to it so it was pretty obvious I had to get on that hill and jump on the rock. After several attempts, I realized that getting on that hill wasn't easy. I tried jumping and going around it and still nothing.
Later, I found out that I had to take an elevator from a completely different part of the area, and move towards the Datacrons like that. And that is when I realized that without knowing where you need to go, you might never get every Datacron.
But now, thanks to the walkthroughs of the SWTOR Datacron guide I used, I have every available one on each planet I visited. Which is also useful at crafting mods. As you can find Datacrons that give you matrix shards. These shards are what you need in order to make the top mods. Combining different color shards will give the item different stats.