Eric,
..snip
>First, never use DataControl. Before ADO we must use them to bind grid, combo, listbox and other but now we can simply say:
>set grid.datasource = YourAlreadyOpenedRecordset

Let me clarify. It's a general term to me: data controls could be DAO, RDO, ADO. I've seen several VB programs, and it seems that per form, depending on the need, these said controls are in the form. What I want to know is the most effective way of accessing data? Is it advisable to just establish the connection once e.g. in the main program just after the user login, and use that connection in the entire application?

>Personnaly, I never use the DataEnvironment (except for using the Query Builder which I use to create queries and I copy the string to my code). All you do with the DataEnvironment can be done by code and this is what I prefer.
>I used to hide all data manipulation in a DLL (which is responsible of the connection). The main application is not aware of the database.

Have you not tried other ways since you started programming in VB other than the above approach? In VFP, there are many ways to access data but personally, the cleanest of them all and effective is the Data Environment: You can relate tables, drag and drop them, set filters, etc.