Great question. As a player who wants to be competitive and well-prepared at a prerelease or as a judge there are several resources that you can use. I've tried to put them in order from "I have 5 minutes and I want a heads-up" to "I'm going to read everything I can about the new cards until it's time to go to bed" (it's the night before a prerelease, get some sleep!). If you've got a long drive and a copilot or driver printing them out and discussing them on the way to the event is a great way to familiarize yourself with the set as well. I'll try to keep this general so these links can be reused for each prerelease.
Note: As I am writing this most of these resources are not officially released for Shadowmoor but will be by week's end.
1. The rules primerThis document contains summaries of new rules and notable changes to the comprehensive rules with the update of each set. It is located on the set's product information page. Shadowmoor's will be available at
http://wizards.com/default.asp?x=magic/shadowmoor/product.
2.The set's FAQThis document contains frequently asked questions about both the new mechanics in the set (which are also covered in the rules primer) and card-specific questions. It (along with the FAQ for many other sets) will be available here:
http://www.wizards.com/default.asp?x=magic/rules/faqs3. Unofficial spoilersUnofficial spoilers are available at a few websites. A few words of caution before I continue, unofficial spoilers are frowned upon by WotC and are prone to inaccuracies. Also the information contained in them often contains information that was illegally obtained or done in violation of policies. Also note that some of the rules interpretations may not be accurate (which is why you should consult the two documents above first. If you do feel that information would be useful, you can find the next upcoming set's unofficial spoiler at mtgsalvation.com
http://mtgsalvation.com/shadowmoor-spoiler.html4. The revised comprehensive rulesWith each new set's release, a new edition of the comprehensive rules comes out to make sure the new cards play nicely with Magic's existing rules. This will include revisions not directly related to new cards as well, so you should always have the latest revision. You can find it at the DCI document center here:
http://www.wizards.com/default.asp?x=dci/doccenter/homeThere may be others such as the DCI judge's forum/listhost if you are a level 1 or higher judge (I'm not sure if they still do that). If anyone has any additions or clarifications to what I've said, I am glad to hear them.
I hope you all find this helpful!
-KD
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