It is very good practice to always have your camera with you, especially when you are in the beginning of your photography experience. However, toting around a DSLR is not always practical. I did make this effort though when I first got my DSLR, and I lived in Tokyo then which means public transportation and lots of stairs up and down into and out of train stations. Still, I did not always have my Nikon with me and I would have to rely on my (faulty) short term memory when I passed by a location I wanted to shoot at. I could have written an address down, but that is not always easy to do if street signs are not visible from where you are. Fortunately, cell phones do actually prove to be useful in solving this problem.
I use the app ShootLocal to record the exact location of spots or subjects I want to shoot in the future. As you can see in the screenshot above, you take a photo with your phone's camera for a visual reference and of course the gps data is recorded with a Google Map pin provided to guide you right back to where you were. It is very handy to have both visual and map data so you remember why and where you wanted to shoot there. You can even add notes, etc about the location. Additionally, locations can be shared publicly and via social media.
ShootLocal is free and can be found in the App Store.