Do you know the best way to implement administrators' login

When administrators need different credentials to login to a SharePoint site, there are different ways to implement it.

1. Obvious "Login" link for administrators:

Bad example: Obvious 'login' link for administrators

2. Use little dot for a hidden link:

Bad example: little dot for a hidden link

3. Use /admin/ to let administrators to login (WordPress nearly got it right with /wp-admin/):

Good example: Use /admin/ URL for administrators