Use the CRM 2011 OData Query Designer tool.
In addition, here’s some examples:
Get Quote details for a specific quote
/XRMServices/2011/OrganizationData.svc/QuoteDetailSet?$filter=QuoteId/Id eq guid'<RECORD_GUID>'
Get specific property details (e.g. ExtendedAmount and Quantity) for a specific entity (e.g. Quote Detail)
/XRMServices/2011/OrganizationData.svc/QuoteDetailSet?$select=ExtendedAmount,Quantity&$filter=QuoteId/Id eq guid'<RECORD_GUID>'
Filter on custom entities and how to use multiple filters
/XRMServices/2011/OrganizationData.svc/QuoteDetailSet?$filter=QuoteId/Id eq guid'<RECORD_GUID>' and new_extension_base_col eq '<SOME_VALUE>'
See codeplex.com