>What is the best practice in retrieving the data of a table and all related reference tables. For example the table [Products] in northwind database and the related reference tables [Categories] & [Suppliers].
>
>Create one dataset with all three tables?
>Create three datasets?

I would say it depends on what you are going to do with the data and how much of it you have.
If you have a parent detail relationship where there are a lot of child records to each parent I would go with separate datasets and pull new detail with each skip through the parent.