It's all about subtletiesEcholocation is all about subtleties, and to understand subtleties, we must first start with what we know.
Start with a control sound. This is your click.
Put yourself in an environment you are familiar with. Pick a room in your house, maybe a small room like a bathroom or large closet. Close the door and make the clicking sound. Listen to the sound. Don't listen for anything in particular, just listen. Try to take in all of the elements of the sound and do it several times so that if you are familiar with it and you can anticipate what it will sound like the next time you do it. This doesn't have to be a long time. Just a few clicks while focusing and listening intently. Now, immediately, go outside and get a good distance away from the building or any other large object and make the same clicking sound.
Did it sound like you expected it to? Did it sound different than when you were in the bathroom? If you answer yes, then you have experienced the effects of echolocation.
Why does it sound different?The click sounds different to you because you are hearing it as it bounces off of the objects around you and comes back to your ear. In the bathroom there are many more objects for the sound to bounce off of that are much closer to you. This creates a "reverb" or very quick echo. When you are not surrounded by objects the sound is much more "dead" meaning you hear it as it leaves your mouth and it does not return to you, hence it does not have the same reverb or echo qualities.
What's reverb? Sounds complicated...It doesn't matter if you don't know what reverb is. The only thing that matters is that you realized that there is some sort of fundamental difference between the two sounds you made. Once you realize that, honing your skill is just becoming increasingly aware of the subtleties in the sound. If you can sense the difference between a bathroom space and outdoor space, then with practice, you can sense the difference between an object 5 feet away and an object 10 feet away. Of course with an infinite amount of practice there is no limit to the differences you will be able to sense.
Enjoy! And welcome to the wonderful world of echolocation.