Need helps for N400 application, thx.

I am about to send off my N400 application, but I still have several questions about that, hope someone can help.

1). What do I send with my N400 application?
2). Do I send both the application fee($330) and the fingerprinting fee($70) on one check or two separate checks? If two separate checks, are both checks with same title(pay to Department of Homeland Security)?
3). Could I send two applications (my and my wife's applications) in one envelope?

Thanks so much in advance for your help.