Great resources here:
Some videos (quality is lacking in some of the older recordings here):
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In order to understand Table Calcs, it is necessary to understand Dimensions vs. Measures in Tableau -- I'd recommend the two videos under "Why Is Tableau Doing That?" from the On-Demand Trainings as good starting points, as they describe some foundational Tableau bits that are very important when learning the tool.
The Tableau 6 Primer is still a good overview for Partitioning versus Addressing:
And finally, this Forum has a HUGE amount of existing threads on Table Calc topics, and solving problems with Table Calculations. With enough study time and practice, you'll start learning.
If you have specific questions, throw them out on the Forums. You'll get a lot of good feedback here.