We have just had our claim for DLA back today and it made me realise that without the help and advice I received from here and another message board we wouldn't have known where to begin with that horrible form.
I thought it might be good to make a list of advice and information for others who are perhaps filling in the forms for the first time.
I would say a really good bit of advice to phone up for your application form, you then get a date stamped form so when you send it back you get the money from that first date you asked for a form - it can make a big difference.
The other thing which really helped was to follow the advice here: www.bhas.org.uk/freeguides/dla_guides.shtml to the letter - it was a very miserable time as you have to focus on all the bad days and hard times but the advice on this site is really good and helps you to focus.
I hope this is useful to someone out there and please feel free to add any other info or links to other websites with info/help.