Put the finished pack of forms away in a drawer at home for a couple of days and forget about it. Then go back to it and with the checklist beside you, work through each and every form and attachment in the order of the checklist, check every single one of your answers. Do this methodically as though you were someone you don't know reading it all for the first time - alternatively find a friend, offer to buy them a slap up meal out and ask them to do the same!
Make sure you have used the 'validate' button on the PDF for any IMM forms that have this facility and correct any validation errors highlighted by it.
Alternatively, find an accredited immigration consultant and pay them a small fortune to do the same