Wrapping up the series on authentication, I'm going to point you over to the Ex Forensis blog for a post by Lars Daniel that deals with his first time testifying as an expert.
"Work Every Case Like It Is Going to Court
A case can take a long time to get to court. Make sure to take copious notes during your examination and to perform a thorough investigation when working a case. Most likely you won’t get a second chance. Since a “do over” is basically non-existent when performing an investigation, do everything in your power to get it right the first time. Can you remember what you were doing a year ago this time? I barely can. Document your work thoroughly so you remember the case you worked a year ago."
Part of the preparation should include researching relevant / recent case law that pertains to the case that you're involved with. Don't depend on the attorney to know this info ... you're the expert. If you have a packet of case law, make sure that you give it to your attorney with plenty of time for him/her to digest it. There are quite a few cases cited here on the blog. But, I can't post everything. If you find something that's not listed here, and you think that it should be ... send it in.