Need suggestions for custom classes

I am nearing completion of my second major database endeavor in VB.NET. I know (in theory, anyway) all about the advantages of object-oriented programming. However, the code I have written up to now works fine just using subroutines, functions, and the standard .NET classes and controls. I have not really seen a need to write any custom classes to do anything.

My question is, aside from creating custom user controls, what are some good suggestions for creating and using custom classes in a database application?

How about making things easier ? or Implenemting new methods to existing classes!