The macro below shows how you can let the user select a single filename:

Sub OpenOneFile()
Dim fn As Variant
    fn = Application.GetOpenFilename("Excel-files,*.xls", _
        1, "Select One File To Open", , False)
    If TypeName(fn) = "Boolean" Then Exit Sub 
    ' the user didn't select a file
    Debug.Print "Selected file: " & fn
    Workbooks.Open fn
End Sub

Sub OpenMultipleFiles()
Dim fn As Variant, f As Integer
    fn = Application.GetOpenFilename("Excel-files,*.xls", _
        1, "Select One Or More Files To Open", , True)
    If TypeName(fn) = "Boolean" Then Exit Sub
    For f = 1 To UBound(fn)
        Debug.Print "Selected file #" & f & ": " & fn(f)
        Workbooks.Open fn(f)
        MsgBox ActiveWorkbook.Name, , "Active Workbook Name:"
        ActiveWorkbook.Close False 
        ' close the active workbook without saving any changes
    Next f
End Sub

Sub SaveOneFile()
Dim fn As Variant
    fn = Application.GetSaveAsFilename("MyFileName.xls", _
        "Excel files,*.xls", 1, "Select your folder and filename")
    If TypeName(fn) = "Boolean" Then Exit Sub
    ActiveWorkbook.SaveAs fn
End Sub

Sub ShowFileOpenDialog()
Dim i As Integer
    i = Workbooks.Count ' count of open workbooks
    Application.Dialogs(xlDialogOpen).Show ' displays the Open-dialog
    Select Case Workbooks.Count - i
        Case Is <= 0 ' no new workbooks opened
            MsgBox "You did not open any new workbooks!"
            Exit Sub
        Case 1 ' add your own code to work on the opened workbook
            MsgBox "You opened this workbook: " & ActiveWorkbook.Name
        Case Else ' add your own code to work on the opened workbooks
            MsgBox "You have opened " & Workbooks.Count - i & " workbooks."
    End Select
End Sub

Sub ShowFileSaveAsDialog()
    Workbooks.Add ' create a new workbook
    With Worksheets(1).Range("A1") ' add information to the new workbook
        .Formula = "Log File for " & Format(Date, "yyyy-mm-dd") & ":"
        .Font.Size = 14
        .Font.Bold = True
    End With
    Application.Dialogs(xlDialogSaveAs).Show ' display the Save as dialog
    If Len(ActiveWorkbook.Path) = 0 Then ' the workbook was not saved
        MsgBox "You can save the workbook manually later..."
    Else
        MsgBox "The workbook is saved as " & ActiveWorkbook.FullName
    End If
End Sub