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You should be able to run anything from the CERN computing workbook, software workbook, and physics workbook.
You also are also ready to use the GRID easily, see instructions here.
Here are lots of handy tricks for getting things done (at SLAC) with ATLAS computing / analysis work.
Make use of the US ATLAS Analysis Support Centers, including their analysis tutorials.
Our old static page has some possibly still relevant but perhaps out of date info.
And there were many good talks at our the 2009 WT2 users' forum workshop.
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