Common sense things:
1) Make sure all forms are the most recent available & signed and dated
2) Make sure all applicable forms are validated & include the bar code page
3) Make sure all questions are answered or N/A
4) Make sure to include the checklist
5) Make sure to include all required documents, proofs, etc
6) Make sure to include country specific checklist (if applicable)
7) Make sure to include payment receipt
8) If additional pages were required for answering questions, ensure they are properly labelled as to which form & question they apply to.
Form specific:
IMM5406
Make sure all of the family members of the Primary Applicant are listed or they will not be able to sponsor them in the future.
IMM5669
8) Ensure
ALL periods in time are accounted for. If even a single month is missing CPC-M may deem it incomplete and return your package.
That's all I can think of for now. Best of luck
