The other day, a friend of mine asked me for some help in trying to find out the host of a client he had just picked up. Which got me thinking, although I would still consider myself new to the trade, I could at least post up some tools that I have used in the past, and still use today for various tasks.
When you register a domain on the internet, no matter what the extension, you need to give your contact details to your domain registrar. These details can be publicly viewed by doing a whois search on your domain. Doing a whois will allow people to know who owns the domain, and how to get in contact with them.