Complete the following tasks to unlock the corresponding achievement. To view your achievements and stats in Steam, select "Community", then "My profile", then "View all my games", then the game and view stats.

Engineer of Goo I: All OCD Flags in Chapter 1.
Engineer of Goo II: All OCD Flags in Chapter 2.
Engineer of Goo III: All OCD Flags in Chapter 3.
Engineer of Goo IV: All OCD Flags in Chapter 4.
Engineer of Goo V: All OCD Flags in Chapter 5.
Executive Producer of Goo Product: All Levels Complete.
Subversive Traveler: There is a secret.
The Architect of Goo: All OCD Flags.