Sometimes the red marker will not be in the right spot; especially if you don't have the physical address to the location. You can fix this. Here's how:
On the main Gmaps page click on "My Gmaps" and locate the Gmap you wish to edit. On the righthand side, click on "Edit Coordinate"...NOT "Edit Gmap"!
On the following screen you can physically drag the red marker to the proper position. Changing the actual coordinates in the edit boxes is not necessary. Then click on "Save Changes" when you are done. Now X marks the spot!