I am now sure for which reasons you want to do a contact print; is it for proofing your negatives or just getting an overview of your images? If your main goal is proofing, check out the link provided at the end of this post.

As Mr. Halfhill writes in his article, you should expose your paper until your blacks are black, not less and not more. You do test strips to not to find a workable exposure for most of your negatives, but to find out when the most transparent part of your negative (the "whitest" part) becomes black on your print.

If you "standardize" your process this way, all of your proof sheets can be compared. Plus, you get some information as to whether you will need to burn or dodge your print excessively, or whether all tones of gray will simply pop out of the developer.

http://www.halfhill.com/proof.html