Multiple Forms - Declare And Instantiate Second Form On Program Start - Use Button Simply To Show Form?

I have a program that uses two forms. The program opens to the Main form, and the user can navigate to the other form from the Main form through use of a button. Here's the way I've currently written it: When the Main form loads, it declares and instantiates the other form during the load procedure. When the user presses a button, the second form is displayed by means of the ShowDialog method. On the second form, there is a Return to Main Screen button which closes the second form, bringing the user back to the Main form.

So, here's the structure of the code:

Code:
Public Class frmMainForm

Dim frmSecondForm As New SecondForm

Private Sub btnSecondForm_Click(blah, blah, blah) Handles blah, blah, blah

[CODE]...

Here's my reasoning: Originally, I wrote the code so that a new instance of the second form was created every time the button was pressed. The problem was that whatever data was displayed on the second form, previously, was lost when the user returned to it a second time. Since the user would be switching back and forth between these forms, frequently, I needed that data to persist.

What is the best practice for accomplishing this:

1) Declare and instantiate the second form on program start, as I have done, and use the button simply to show the form?

2) Declare and instantiate the second form each time the button is pressed but maintain the variables on the Main form and pass them ByRef to a custom constructor for the second form? Is this even possible?

3) Something else?