How to create a VMware template

Yes and it is simple and you can do it even without vCenter. Open vSphere Client, select your VM (it has to be powered off), go to File->Export->Export OVF Template... and save it to your local drive. When you ready to create VM from it just do it through File->Deploy OVF Template.

On ESXi? Yes.

On a standalone, free-license ESXi device? No. You need vSphere Server (nee Virtual Center) to create templates.

On the free ESXi you can enable Tech Support Mode and then once that is enabled you can connect to the host via SSH and use:

vmkfstools -i source.vmdk dest.vmdk -d thin

Then you can create a new VM using the file just created as an "Existing Disk".

It's not as convenient as as a Template, but it's better than nothing...

Yes you can.

In Virutal Center right click on the Virtual Machine and select Template -> Convert to Template.