Basic requirements
Basic requirements for a competitive DA application are actually pretty simple. You need a competitive research plan. Minimally, it has to do the following things:
+ present the topic of the research and its research question
+ justify why the topic is important
+ possibly, describe the main hypothesis
+ tell in detail how the problem is researched, and why the answer produces a valid answer that the reader can trust
+ in addition, you may need to think about ethical issues, esp. when studying children, seniors, or patients
Technical parts of the plan are like in any project plan: schedule (plan for 4 full-time years), budget, etc.
Keep in mind that the difficulty lies in details. Outlining the topic is crucial, but often a few sentences are enough. Justifying the topic, on the other hand, requires lots of more work. In essence, the plan has to show