I thought I'd branch this topic off since it seems to have generated a lot of interest. Unfortunately I know zero about this so I can't offer any tips from experience, but here are a few interesting links from around the web to get us started. Hopefully some of the more experienced folk can help us.
It seems like a few folks would like a little more 'bicep ease' -- I don't know if that's the right word for it. The blouse or dress fits fine sleeveless, but then feels a bit tight across the top of the arm when you're swinging your arms around. I have noticed this in almost all of the RTW woven shirts I have.
http://www.threadsmagazine.com/item/5052/on-fitting-sleeves/page/all
http://sewingfantaticdiary.blogspot.com/2008/09/sleeve-bicep-alterations.html
http://nancyksews.blogspot.com/2012/01/fitting-with-kenneth-king.html