During the majority of cut scenes while you're playing as Altair, you will sometimes see the screen 'glitch'. You will see a bunch of hexagon-shaped molecule diagrams flash quickly on the screen.

Pressing any button will make the scene cut to another camera angle. These are the glitches.
Constantly tapping any button during every cut scene will make sure you hit at least 85% of the glitches.
If you get every glitch, this achievement should unlock.