Just about everything is scannable in the world of Metroid Prime Hunters. Much like the GameCube titles, Samus' Scan Visor can pick up detailed analyses of objects, creatures and lore scattered through the Alimbic Cluster. You can access your electronic journal of recorded entries from within Samus' gunship.
When you greet a scannable piece, tap and hold the circular reticule at the base center of the touch screen to fire up the Scan Visor. Look for a small square icon hovering above the object, then hold L to engage and complete the scan, locking the item away snugly.
Each object resides in one of three categories, of which are already filled out with a finite number of blank entries. As you fill up the Logbook you'll see entries filling in the blanks in alphabetical order.
Scanning those trickier hostiles can summon quick tips to deal with them, especially when encountering those pesky rival hunters. Make certain to scan all the forms of the Cretaphid and Slench guardians, as you'll only have one shot at each one. You'll be free to scan the rival hunters (just track one down when they randomly move about each celestial location) and the multiple forms of Gorea (the final boss) more than once. Unlike previously the game will retain all of your scanned entries even beyond completion of the game.
Below resides a complete listing of all the possible log entries and where to find them. They're all set out in alphabetical order exactly as you'll find them in the game, so use these lists to see which entries you're missing. Objects set with a * can only be scanned once, so don't miss them or you'll have to start over if you want a 100% rating.
Special thanks to Pixelate for clarification about the Electro Voldrum scan!
Note: The locations of Hunters and their alt-forms are listed according to initial encounters.