IT Is going to be mainly trial and error a far as positioning goes, it is also going to depend on the font and wether or not you are using a Generic/Text Driver (if so the character spacing, line spacing and font are what ever the printer has been setup for). Back in the DOS days you could send out individual characters to the printer but printing in windows is page based meaning you will need to use the PrintDocument Class, handle the PrintPage event using the PrintPageEventArgs Graphic Property's PrintString Method to position the text where you need it to be.
Something like this:
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
If PrintDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
PrintDocument1.Print()
End If
End Sub
Private Sub PrintDocument1_PrintPage(sender As System.Object, e As System.Drawing.Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
e.Graphics.DrawString("Hello World", New Font("Arial", 10), Brushes.Black, New Point(100, 100))
End Sub