We like to find undervalued domains with an eye to building a useful site. To this end the domains we have undeveloped are usually given a holding page rather than parked. This allows us to optimise for the keywords and get our own data. The data lets us find those domains that get the best natural traffic go to the top of our list to develop.
Other domains we have that we feel are good for branding. These are the ones we are happy to hold, but would rather work with someone that is looking to build a business around them.
We are UK based so most of our domains are .co.uk.