Every grant and fellowship program comes with many pages of rules, regulations, guidelines, criteria, ... How carefully should you read them? What can you learn from them?
I have two separate points.
First, as the applicant it is your responsibility to read and to take note of these regulations. This is time consuming and boring. But it is still your responsibility. Don't expect or demand someone else to do it for you. It is not the responsibility of your supervisor, department chair, local research administrator, group secretary, or the funding agency. Don't ask questions when the answers are there in the rules if you actually read them. And don't ignore the rules. For example, if it clearly states you have to be 5 years past your Ph.D, don't apply anyway if you are 3 years past your Ph.D. This may seem inane to some readers, but it does happen. Also, just because it says you can do something does not meet it is a good idea. For example, with regard to budget requests, you may be allowed to ask for $1 million over 5 years, but if you look at the successful applicants you will find almost all get about $300-400K over 3 years.
Second, if possible find out the real inside story about priorities and preferences from the people who actually make the decisions, e.g. someone who has served on the relevant committee. Many grant and fellowship programs will make claims about priorities or preferences, whether it is for specific research fields, women and minorities, renewable energy, early career researchers, national citizens, ..
However, this is sometimes just platitudes and was inserted in the guidelines to sound good or to pacify someone. Don't get your hopes up (or down) if you do (not) fall into this sub-class of applicants. On the other hand, sometimes these are real priorities and if you don't meet this criteria you are wasting your time applying.
Also, not all parts of the application are equally important. Some applicants agonise over preparing sections that actually receive little scrutiny. I know of one program where the actually scientific project and the letters of reference get virtually no attention. It is all based on the CV. The only way you will find out what does and does not matter is to talk to someone.