Set `vtp mode transparent` to disable VTP on a switch. If VTP version 2 is used, a transparent switch will still forward VTP advertisements, but, in any VTP version, the transparent switch will itself ignore VTP.
The VTP domain name and password must match between switches for VTP to work, and blank (null) VTP domain names and passwords are valid, so any switches set this way will exchange and use VTP advertisements.
VTP only travels on trunks. You can connect switches with access ports but VTP will not propagate across these ports.