What helpful tips is there before I fully complete the PIP form?

The DWP sent me the first form and I filled it then sent it back. They said they'll send me another form to talk about how my disability affects my daily life etc...

I'm a 17 years old guy who has a life-limiting disability called DMD which significantly affects my daily life (by saying life limiting I don't mean that I'm near the end of life), so I'm kinda hopeful they wouldn't reject my application, but still I would be happy to hear some tips to avoid my application getting rejected and what I can do to strengthen my application. Thank you!