Consider the following scenario:
You have a logical network that has two VLANs defined: One is VLAN 0 and the other is VLAN X.
When you create a virtual machine using System Center 2012 Virtual Machine Manager and assign it to VLAN 0, when you view the properties of the virtual machine you notice that it points to VLAN X.
If the VLAN are not for the same use you may want to create two different logical networks, one for each VLAN. By doing this, once the logical network is assigned it will select the only VLAN listed for that logical network.
When deploying the VM from template when you choose Static IP address from pool the process will auto select the vlan based on the pool selected. This helps control the VLAN for the VM.
If you create a VM and use DHCP the recommendation is to create a seperate logical network for each vlan. This way the same vlan is assigned everytime.