Annie,
One of things I found that helped me to have a better understanding of the ITTO's was to make multiple copies of page 61 out of the PMBOK guide and highlight different ITTOs on each page (Got this idea off of a PMP study blog). For example, I have included an example image of what I did for Organizational Process Assets (i.e. OPA's). The processes that had OPA's as input are highlighted in yellow and those that had OPA updates as output are highlighted in blue. This helped me to better visualize the relationships between the ITTOs and processes better. I did this for a variety of ITTOs that caused me the most difficulty. It was interesting to see the patterns revealed when doing this and that was also helpful in gaining better understanding of the relationships.
I also used some
free Ipad apps which were also helpful. They are ITTOsApp and PMP ITTO (a.k.a. PMP ITTO game). If I was smart enough I would have loved to have been able to write an app to do what I did manually. I think that would be pretty helpful. There are also some "flashcard" type apps as well but I didn't find those as useful.
I know most say not to memorize the ITTOs and in general I would agree. However, I did spend some time memorizing ITTOs for certain knowledge areas that were troublesome for me (e.g. Quality, Risk and Procurements). For me, there really were not that many specific ITTO related questions on my exam where you were asked to identify which particular ITTO was related to a particular process. They were more wrapped up in the situational type questions which made it more challenging. So, it is certainly more important to develop a good overall understanding of the relationships.
Keep working at it. You can do it!
Best of luck,
Mark