To transfer a domain with .com, .net and .org extension you have to follow a simple procedure.
First, check if your domain has a "Lock" or "Active" status with your Registrar. To check it you can make a Whois clicking here.
If your domain's status is "Lock" ask your Registrar to turn it into "Active", to transfer your domain. The transfer cannot be processed if the domain has been transferred in the latest 60 days or if is expired.
The change of status allows you to process your domain transfer. You will get an email from your provider which will confirm you that the transfer is in progress and the possibility to stop it by clicking on a dedicated link inside the email itself.
Then, you just have to wait for the transfer to be completed.