There are lots of questions around this general area, but I haven't seen one that exactly mirrors what I'd like to know. It's per the title really. My understanding (and what I'm told by my host) is the easiest thing is just to get the transfer key and bring the DNS across to my own hosting provider. Also I'm told by my host this doesn't affect the client's ownership of the domain itself.
Basically, I have a subdomain setup with the site (this has the same IP address as the top level domain). So presumably just giving the other registrar that IP address will only refer it only to the TLD rather than the subdomain.
What's the easiest way to achieve this? It's an asp.net site, I don't have a hosted directory on the client's account where I can code a redirect.