In Google Maps if you long press a point on the map you will get a location bubble. If you press on the bubble it will open an action page which has a greyed out star top right - press the star and it will turn yellow/orange and you have then set that location as one of 'My Places'. The location will be starred on the map and will appear in your list. Naturally in built up areas it is very accurate for navigation, off the beaten track it will give the nearest recognisable address or feature. It is possible to navigate using lat/long co-ordinates, just enter them for your 'end point'.
To clear a starred location from your list/map press the star and it will return to greyed out.
I have just downloaded Locus Pro which, for