As customer requirements in regards to reporting become more and more complex, you need to make sure you are aware of the Lookup and LookupSet
Lookup / LookupSet allows the report to retrieve an item or a set of data from another dataset in the report, it is very simple to use and I wouldn’t of been able to complete certain reports without it.
It is particularly useful when you are trying to access a lot of data from multiple tables (especially M:M relationships in CRM)
This feature is only available from Business Intelligence Development studio 2008 R2