My First Blender Plugin refs: http://cgcookie.com/blender/2013/05/23/creating-custom-menu-python-scripting/

my_custom_menu.py

bl_info = {
        "name": "My Custom Menu",
        "category": "3D View",
        "author": "Joshua Zhang"
        }


import bpy

# Define a custom menu
class customMenu(bpy.types.Menu):
    bl_label = "Custom Menu"
    bl_idname = "view3D.custom_menu"
    
    # Define the operators and functions
    def draw(self, context):
        layout = self.layout
        
        layout.operator("mesh.primitive_cube_add")
        layout.operator("object.duplicate_move")
        
def register():
    bpy.utils.register_class(customMenu)
#    bpy.ops.wm.call_menu(name=customMenu.bl_idname)
    
def unregister():
    bpy.utils.unregister_class(customMenu)
    
# Ensuring register the menu only when this script is triggered in itself
if __name__ == "__main__":
    register()