Make sure you understand an assignment when you receive it. Ask for clarification if necessary. (Hat tip to Prof. Kenny.)
Observe all deadlines, and warn the assigning attorney as soon as possible if you think you will miss a deadline.
If you are not familiar with an area of law, you may wish to consult a legal treatise on the topic.
If the assigning attorney says "look at Collier on Bankruptcy," do so. But you may also want to consult the "new" online Bloomberg Law Bankruptcy Treatise to see if you can find additional, useful information.
The websites for most federal administrative agencies can be great starting points for federal regulatory research.
FDSys offers free access to the U.S. Code, Code of Federal Regulations, and other resources.
The Legal Information Institute offers links to free state codes (statutes). Of course, if your institute has a flat-rate Lexis or Westlaw contract, use the respective version of that state's annotated code to find related court opinions and secondary sources.
Respect your ignorance.
Ask for clarification if you receive an assignment that is unclear.
Make sure the legal sources you cite are still "good law" -- Shepard's, KeyCite, BCite, CaseCheck+
Don't miss deadlines.
Start with a treatise or legal encyclopedia when researching a "new to you" area of law.
Don't lie, cheat, or steal.
Treat administrative assistants (and all colleagues) respectfully.