Recently, I have got chance to work in Matching rule for Account, Contact and a custom object.
Have a look at these videos to get an introduction about Duplicate Management and Matching rules:
http://salesforce.vidyard.com/watch/PdYJPLbTqiI-kCXlWrr32w

Few points to note:

a. A matching rule can have only one lookup relationship field.
b. We cannot have a Date field in the matching criteria. Work around is to have a text field which has the date in text format and use it in the Matching Criteria. Suppose, you have a DOB field and to use it in the criteria, create a text field which will hold the date in text format. You can have a workflow to update this field when DOB is not empty(use TEXT() function).
c. We cannot have multi select field in the matching criteria.

Please let us know your comments.

P.S: When you use TEXT function, Dates are returned in the form of YYYY-MM-DD, that is, a four-digit year and two-digit month and day.