This video series by Microsoft will visually walk you through common data access scenarios when creating a three-tier architecture.
#1 | Data Access Layers in ASP.NET Applications 11 minutes, 50 seconds
#2 | How to Manually Bind a Dataset to a Datagrid 7 minutes, 28 seconds
#3 | How to Work with Datasets and Filters from an ASP Application 6 minutes, 1 seconds