A few things that come to mind that I appreciate in people’s applications:

• apply to several funders where possible
• try and point to a concrete plan (even if it’s basic)
• talk about any tests you’ve done for your plan already (e.g. have you spent some time trying to upskill outside of a grant)
• talk about why a grant is better than applying to a program/internship/job (or it could be that it’s worse, but you aren’t ready to do those alternatives yet)
• try to talk about an end-to-end theory of change for your work - this is mostly about showing you’ve thought about how this project fits into a larger plan and you’re thinking strategically about your career

To be clear you don’t need to do any of these things to get funding, but I often find that applications are improved after people consider some of these bullet points.

You likely won't be applying to the Meta Charity Funders for this project, but I think that they have pretty good general tips on how to approach writing grant applications. This forum post has some of the key points. 

I like Caleb's answer. Some more thoughts

• Clearly writing out the evidence that you're a good candidate for the grant. This can look like conventional credentials, past projects, references, etc, just anything which increases my probability that it's a good idea
• Scoping out the purpose of the grant. In particular, I generally expect that when someone without a track record of AI Safety/similar research does an independent research project, it's fairly unlikely to actually result in impactful research (doing good research is really hard!), and that most of the impact comes from helping the person skill up, test fit, and either get a job or do better projects in future. You tend to skill up best when making a sincere effort to do good research, so this doesn't mean don't think about it all, but I would also discuss the skilling up benefits to you and why that matters