How to connect to new Mac Mini Server without keyboard/display ?

you need either apple remote desktop admin

which is available in the app store

or use apples inbuilt screen sharing

For ARD

you'll have to enable remote management on the server

system preferences, remote management

choose a local user i.e. the admin user

set what privileges you which the remote user to have

when you connect to the server from ARD you'll be prompted

for user name and password, which is the user name and password

for the remote management user you have setup on the server.

if the connection is refused look in ARD all computers either delete the entry and scan for computers. or edit any pervious entry (right click get info) and enter the correct username and password

if your running ARD admin as a normal user some functions may not be accessible

you'll have to login as admin user on the ARD admin machine start ARD go to ARD preferences and give whatever privileges to none admin users you require

e.g

none admin users:

full access to all features

access restricted to the following features

local network scanner

network address scanner

file import scanner

etc.