A domain's worth will depend greatly on the following factors:

Traffic levels - expired domains will often still get good levels of traffic despite having no content whatsoever. As any webmaster will tell you traffic is the lifeblood of internet success so lots of traffic will mean a higher value on a domain.

As you look for domains be sure to keep one eye on how much Google Adsense is paying for clicks on text adverts related to that keyword. Then you can easily build content rich sites using whypark.com to automate the process for you. This leaves you more time to find those valuable domains.

Page Rank - if you intend to sell links on a website then the Google Page Rank of a domain will dictate what you can charge per month.

Inbound links - these, Page Rank and traffic all go hand in hand so finding a domain with lots of quality inbound links will again lead to a higher valuation.

1. First you will need to find all of those domain names that have expired recently. To do this you should use Drophunt. To find all expired domains simply select exactly in the search field and leave the box blank.

The results will show you the domain along with it's Alexa rank, Google Page Rank and number of backlinks in MSN and Yahoo. I don't always trust these figures so I use the tool in step two.

2. Using Check Page Rank you can enter a domain and find out whether or not the Page Rank is valid or not. The tool will also give you a much clearer picture of the actual number of backlinks to a domain. If the Page Rank comes back as forged then leave that domain alone.

3. Finally, after you have found a potential domain that has valid Page Rank, check to see how that Page Rank varies across over 700 Google datacenters using Dig Pagerank. The reason this is important is that if the Page Rank is higher in some datacenters than others, at the next Page Rank update, it is likely that the Page Rank will move up or more likely down. So look for domains with stable Page Rank across datacenters.

Once you have registered a valuable expired domain there a a few different things you could do with it.

1. Sell it - if you are looking for a quick return on your investment then sell your new domain name on one of the many domain marketplaces.

2. Park it - if you want to hold on to your domain but don't have the time to develop it then you could do what is known as domain parking. This basically means a third party company will host a simple one page site loaded with PPC adverts and you will earn the lion's share of the revenue generated from them. whypark.com does something very similar to parking but gives you more control and more potential revenue in this reviewers experience.

3. Develop it - if you really want to make the big bucks then you should think about developing a website that fits the domain name. This could be anything you like and the existing flow of traffic should give you the motivation to grow it and earn more. Again, you could use a cheap, effective and time-freeing program such as whypark.com to put this process into overdrive.