...35 developers, 15 business analysts, and about 10 QA...
Unit tests and integrated builds - are ABSOLUTELY MANDATORY... As the application gets larger and larger it becomes almost impossible to add new code or refactor existing code without going through tests.
We originally had longer iterations - one-month ... had problems estimating [large stories] ... We are now doing two-week iterations ... estimations are closer to target....
Have an iteration planing meeting at the beginning of each iteration where the customer and developers split up in groups all day to discuss the latest story cards and estimate them. At the end of the day regroup and present your estimations and findings... This will keep the whole team in-the-know ... without burderning everyone with an extremely tedious and long meeting.
Frequent design meeting (lunch...) are very helpful....
It will always be tempting not to refactor and to just patch a solution, but if it is patched too much the team will be forced to make major refactorings later on.
...a group of individuals are needed to be the customer....