Instructions
Know what to look for. Jedi Holocrons are bright yellow glowing cubes that are about half the size of your character, Starkiller. They are free-floating and do not move, though their "aura" does shimmer a bit.
Look behind crates. Most notably in the TIE Fighter Factory level, Holocrons have a habit of hiding behind stacks of crates and power generators. Either throw them aside with Grip or blast them out of the way with Force Push.
Look around. Nearly every area in every level has a set number of enemies that spawn in. Once they are all defeated, you are free to look around. Do so and you will quite often be rewarded with a Holocron or two. Make sure you look up. Nearly all Holocrons are hiding above normal eye level.
Ride the elevators. Many Holocrons are set at the top of large structures. Use elevators or junk piles to jump up to them. You may also have to bend large pieces of metal or move objects into place to get at certain Holocrons.
Open every door. There are several Holocrons hiding behind doors which you can blast open with Force Push. This is particularly true on Kashyyyk, in the TIE Fighter Factory and on the Death Star.