Image via WikipediaI'm working on getting used to the "Blade Pop" click. (See article on "Analysis of Different Clicks") I find it is a good idea to perform the click as you walk around. When you're clicking just listen to the sound of the click. If you are seeing, then feel free to keep your eyes open, if not then observe in the best possible way, the nearest object and listen to the sound and how the sound changes as you walk around and move from object to object or from room to room.
After doing this for a while you'll start to notice the slight differences in the sound, and you'll be able to make little tweaks in order to improve it. (See article: "Properties of a good Click") Even if you don't think you're noticing, you may very well be subconsciously learning, as a great deal of echolocation is achieved by subconscious recognition. You can change the frequency by changing the shape of your mouth, and if you continually make the sound you will just get accustomed to it, and gradually it will become easier to use it for echolocation.