If this is your first playthrough you can see faint fractures in the veil as soon as the Golden Road location. You cannot interact with them until you've acquired a Vinculum, which you do upon reaching Cahlabrok. However, you can make a note of the locations the first time you see them, in case I've missed any in this guide. When you have a Vinculum, make sure to always have it equipped since that makes the fractures easier to see.

Cahlabrok
*The crypt where you acquire the Vinculum has 4 fractures.
*Following the main quest, you'll interact with 5 fractures while figuring out where Saorebh went.
*Upon returning to Cahlabrok from the Crimson Mire you can start a quest to deal with the undead in the former Commune, the quest starts in the south eastern part of the actual town (not the lower part with the mushroom farm and graveyard). You'll find one fracture inside the Commune building (merchant), and one on the western part of the courtyard of the Commune (vengeful spirit quest).

Crimson Mire
There is a fracture just at the beginning, in a small arena. Reveals an orc champion that quickly turns hostile.

The Golden Road
*A single fracture is found just north of the starting point, at something similar to an altar. It reveals a Claymore of Inevitability that might be a bit hard to pick up due to the small area that is clickable.

Windwall Outskirts
*One very close the the beginning of the area, just before the first bridge. Reveals a merchant
*One close the the northwestern part of the map. Might need to start "A noble quest" for this to be possible to interact with. The quest is started by talking to a woman on the southern part of Greykeep King's Vantage, between the merchants.

Silver Drift Hollow
*There are 3 fractures in the area very close to the godstones, revealing pressure plates on the ground.
*There is one fracture to the southeast, revealing a hidden chamber containing both a set of reavers (you might want to wait until you actually get the quest from the noticeboard before killing these bandits, to not mess up that achievement)
*Finally there is another fracture in the hidden chamber, also revealing a pressure plate. Placing a character at each one will open the crypt and allowing you to burn the body of the vengeful spirit

Scorching Desert - Oasis
*A single fracture a bit east of the oasis reveals a merchant.

The Eye
*One fracture close to the beginning of the map shows a merchant
*A fracture further spawns Sentenza Noria, which quickly devolves into combat.

The Amber Lake
*One fracture in the northeast of the map - merchant

Leonidar Gorge
*A fracture around the center of the map - merchant

Old-Hâlu - Narthex
*The fractures hide the books required for the quest.
*One fracture to the east by the pressure plate/light puzzle, spawns a pressure plate necessary for solving the puzzle.

Old-Hâlu - inner area
*One fracture very close to the second godstone - merchant
*Another fracture just by the last godstone

King's Crossing
In order to enable the fractures in this area you need to start Yria's personal quest. It's unlocked by a conversation with her after having been to King's crossing the first time. It might be hidden in the conversation options, but if the first conversation option is [2] then click [1] and it should start the dialogue
*There are a total of 4 fractures in this location, all marked by the quest.

Windwall cave
A fracture opening up the north passage to the reavers

Old Monastery
In the south-western area between the shacks is a single fracture - merchant