This application can help you to remember those locations. It will display on Google-Maps your position at a given date and time and let you record that place.
So, press the "Remember my current location" button and enter an optional description for that point. Make sure the GPS is on and your Android phone will save your location.
Then, when you need to find that place, press "Show saved location" (you can select one of many you saved) and the application will show you your current position (blue mark) and the saved location (red mark) on Google-Maps.