It is best to travel light in Vietnam. One medium sized bag and a day pack will provide more than enough room to carry everything you'll need to survive for one month, and still have enough space for the things you'll buy in Vietnam.

There is extensive consumer goods in Hanoi and Ho Chi Minh City, so do not worry about running out of or forgetting something.

Here is the checklist before your departure from home to Vietnam: http://www.footprintsvietnam.com/Travel_Tips/General/Before-you-leave.htm