I cant remember my form... do you mean the first question where it asks what your conditions are & how they affect your life?
If so..
We just gave an honest explanation of all the ways in which my condition affected me - eg list of symptoms, what I had to give up & why - so I included all the things that I enjoyed doing that I can no longer do. Including examples. (I think if you illustrate that you had to give up all kinds of things that you loved doing as well as work, it shows you don't have 'convenient' symptoms.
And yes I included my diff conditions - but only ones that affect my ability to do the tasks covered in the form. So for example I have some gynaecological conditions but I had them long before ME & since they do not affect one's ability to work, I left them out.
Also, since you could give scores of examples of how it affects you/what it prevents you doing, & there's only so much room on the form, I focussed on the details & examples which actually cover the questions/tasks in the rest of the form - those which I believe I qualify for the most points on - so don't choose an example/detail of something that makes your life miserable but isn't covered by any of the activity questions on the form over one that does.
So of the 1000 things you've had to give up/can no longer do, include the ones that involve both standing, walking, sitting, starting & finishing tasks, communicating etc etc etc, rather than one which covers something not in the form.
It should be a short, honest, 'this is what getting ME did to my life & why life with ME is so shit' write up, but always with the actual questions they ask in the rest of the form held in mind - otherwise you could go on for 20 pages & still not say much that's relevant to the actual questions about walking etc.
It's an attempt to explain what the experience of having ME is like, plus the specific ways that it affects your day to day life.
ETA also be wary of anything that could be ambiguous or be misinterpreted, or incorrect assumptions made about it. Proof read it with a judgemental, sceptical/disbelieving person's attitude, & then modify/remove/explain.
EG if you are rarely well enough to go out but 'X' happens when you do.... include the full 'I am rarely able to go out but when I do X happens', instead of just saying 'when I go out 'x' happens' because they may choose to wrongly assume from the latter version that you go out every day.
I don't claim this is right, but it's how we approached it. We were successful but I wouldn't know whether this was why. Who the heck knows!