As VB.NET is object orientated, which is the better practice when referencing objects which are regularly accessed such as forms or an SQL connection?

- Declare the objects at a Public level so all properties remain the same due to a singular instance? (is there a memory issue in doing this?)

- Declare new instances of the same object at a module-level as and when needed?

Thanks.

p.s. any other object tips are very welcome.