DNS troubleshooting Techniques

[Jmelanson]

Hello everyone, I am currently learning about DNS and troubleshooting techniques for a job I am hoping to get. I know very little so please be easy on me I need to know the following
1. finding authoritative name servers
2. how to use nslookup(or dig) to look up specific zone records ( A, and/or MX ) from the authoritative name servers
3. I also need to know about DNS caching and why its important to look up DNS answers from the authoritative name server.

if you could help me out with any of these, it would be greatly appreciated. Thank you.