It all depends on your registrar and if you want to transfer to another user at the registrar or a person using a different registrar. In most cases the registrar will have a transfer guide on their website so your best bet is probably to contact the support at your registrar.
Domain transfer is a process in which you can transfer your existing Domain Name from its current Domain registrar/hosting company to another Hosting company/ registrar. During this process, if the website is Live, it remains functional.
A more direct way is to transfer within the same registrar. Better to ask the receiver of the domain to create an account with the current registrar you are with.