Petre,
The ITTOs are useful to know, but don't go overboard on memorizing them. There aren't all the many questions regarding them on the test, but rote memorization will sap your capacity to study for other areas. I found it far better to understand the process charts at the start of each process; these will logically show you how each process interacts with each other and you may just happen to learn the ITTOs via osmosis. Good luck!
- Steven