I would also like to add few things which is based on my experience while I was learning system administration (Windows Server 2012).
This is how I proceeded:
1. Acquired training from Microsoft certified instructor
2. Followed Mark Minasi’s book
3. Practiced a lot and when stuck, asked for help from 4sysops forums
4. Appeared for exam certifications
5. Tried and learnt by helping other users on different forums like Technet