To push a domain name to another user in namecheap if that domain is registered at namecheap do the following.

Login to your namecheap account.
Click on View Domains.
Click on the domain name you want to push to another user.
Click on the link on left side which says "Push Domain To User"
Enter your existing password, The new owner's username and select proper settings and click on the "Push this domain to other user" button.

For users who are receiving the domain name in namecheap there is nothing to do. It will directly fall in your account from the senders account upon successful push.

The above information is for smooth transactions for domain name buyers and sellers on nameslot.com

For more info you can go to the namecheap.com's help section.

Thanks.