Hi,
The most reliable backup will be with the Virtual machine shut down and VMware Workstation shut down as well and then copy the whole folder that your VM resides in.
If you have to keep VMware Workstation running (not a very big deal) at least shut down - not suspend- your Virtual Machine.
A snapshot is not a backup, it's a differential file, useless without the original base disk.
If you want to only copy disk files, then pay attention to copy every .vmdk file.
But all of the other files are really small, it makes little sense to skip the non disk files.
There are a few alternative ways, but that requires that you actually know very well all of the down sides of doing it differently.
--
Wil