There are three categories of client-side error:
Report errors are often due to missing information. For example, the report template and all necessary datasources (and any data files) are not deployed to the server, or are not deployed in a consistent location (remember in particular that the Repository is case-sensitive). You should also check that the dynamic parameters passed in to the render engine are correct. It is usually advisable to include default values for the parameters, so that it is easy to verify the report by not including any explicit dynamic parameters.
After rendering a template for the first time or after any change, you should check the server log for any JavaScript errors while running the report, to ensure that all information is rendered correctly and efficiently.
Datasource errors are different for each kind of DataSource: