Premium Domain names are domains that are already registered, but are available for sale at a higher price. Sometimes it will be an individual selling the domain, or it could be the domain registry (Like Donuts Inc. or Radix) selling their top quality inventory at a higher price point. These domains can be priced anywhere from a couple extra bucks to millions, depending on the domain name, the level of interest, or the amount of traffic it organically receives.
In order to maintain ownership of a domain, you must renew it yearly. If you don’t, it “expires”. An expired domain goes through several stages before being released again for general registration. The process differs slightly from one registrar to another but it’s more or less the same. GoDaddy explains what happens to domains that expire with them here.
Get appraisals for your domain names. When selling, you will want to know what kind of price you should expect to get for your sites. There are a variety of websites that offer free appraisals for valuation. This includes larger domain auction sites such as Sedo.com, GoDaddy.com, and DomainIndex.com. These of course are only estimates, but they can give you a good idea of what certain domains might be worth.
Wait for people to contact me: When I bought my two domains, I didn’t pay the extra $12 for Domain Privacy, learn about Domain Privacy here, so anyone can look up the owner of IHateCold(.com) and ReallyFunnyJoke(.com) in the ICANN WHOIS Database. It can tell you whoever owns any website unless that domain owner pays for domain privacy. So if someone was really interested in any of my websites, they could look me up and shoot me an email about their interest.