What is the best way to get in contact with a Lego expert? Catawiki is looking to hire a Lego expert to estimate the value of offered sets and arrange its weekly Lego auction. Where and how could we find people who might be interested in such a position?
An effective way of contacting LEGO hobbyist is either by..


Contacting Local LEGO User Groups or similar hobbyist associations


Many countries and areas have their local associations. For a map of regional associations, see LEGO Ambassador Network's LUG map. By contacting representatives of association, you can easily contact local help.


Requesting help from online LEGO forums


Another option is to post a message at online LEGO forums. There are many forums as some are theme-specific and some are area- or language-specific and thus it is hard to pinpoint exactly which forum one should try; it depends on the case. Safe bet would be to post in few of the global online forums, such as Eurobricks.


Contacting individual hobbyist via site/blog/email


If one wishes to contact particular hobbyist, a good way is see if that particular hobbyist has own blog or similar page. Even gallery services such as Flickr often contain email which can be used to contact the hobbyist.

For this particular case, I would advice posting a message at Eurobricks since it has particularly large amount of readers.