You get this achievement for successfully doing hidden object puzzles 1200 times.
Yes, that is correct...1200.
There isn't really a way to farm this, you simply have to keep on doing the puzzles. If you're going for all of the achievements, you'll eventually get this before you get some of the others (e.g., exploring specific locations a large number of times), so while it may seem painful, it's actually not as bad as some others and will just come with time.