It's tricky, because with query tuning the answer is always 'it depends'.  It depends on what your trying to do.  To cover things that may or may not apply to many in the audience, it gets generalized really fast.Be careful with Cartesian products, be careful with correlated sub queries, be careful with joining on calculations.  so vague.  And there are so very many blog posts by excellent writers that cover these things.

I do agree with Jeff Mlakar, paid conferences are much harder to expect organizers to consider apprentice or journeyman attendees that don't have access to Enterprise Edition, and are just looking to code better.