I followed this procedure and may not necessarily be correct and do not know if it helped either. I assumed that the person opening the application packet would be overworked and underpaid, so I ended up making it easy for them.
- A cover letter along with the N400 application
- US postal service with overnight delivery (no return receipt is necessary ~ you can track this online)
- Every attachment sequenced and cross referenced by the cover letter
- I had completed the application form using the adobe fillable kind form, so everything was easier to read
- Check and re-check your application and supporting documents
- Submit one check for both app fee and biometric fee made payable to USCIS
- Keep your fingers crossed until you obtain your citizenship ~ cause Murphy's law will come true
Good Luck to you!