Visualization is the most direct path to lucid control I have found. There are a few ways I use it and several ways to practice.
1. The VILD technique can be used before bed to imprint a visual experience. You simply imagine being in a small room with a single door. If you imagine it and focus on it enough while going to sleep, you will likely wind up in that room during a dream. Because you had visualized it (preferrably with the intent to become lucid), you will remember that you made this room and it will hopefully trigger a lucid dream.
2. Visualization can be combined with [ADA \(sidebar\)] (http://www.dreamviews.com/f49/all-day-awareness-dild-tutorial-kingyoshi-113253/) to increase your general level of awareness as well as to get used to the idea of manipulating your environment through imagination. I will often practice ADA while at Disney with my wife. And visualization comes into play when I imagine random people doing silly stuff (like skipping around, or pushing Goofy over).
3. Once you actually become lucid, you can use visualization to actually control your environment. I made a [large post about my findings](http://www.reddit.com/r/LucidDreaming/comments/1h5ca5/visualization_is_the_true_key_to_dream_control/). Basically, this visualization technique utilizes the expectation principle. When I visualize someone about to walk through a door or imagine myself holding a shotgun, I don't just expect these things, I manifest them. Since dreams are driven by expectation (even if it is subconscious), being certain something exist due to visualizing it pushing expectation as far as it will go. I am not just pretty sure someone is about to walk through that door, I am watching them do it until completion.
4. Recovering from SP or Advanced FILD: [I was once stuck in SP](http://www.reddit.com/r/LucidDreaming/comments/130jcd/survived_sp_and_was_able_to_enjoy_my_first_wild/). I couldn't move or call for my wife. Instead of freaking out, I imagined a visual experience. I was just at a party talking to a bunch of people eventually, I was able to actually hear what they were saying, then I was actually at the party. If you don't know how to effectively visualize, you may find yourself having trouble with SP.
Visualization is an incredible tool in the world of lucid dreaming. I have found that it requires a significant amount of effort to be able to have total control. At first, I could only imagine a single image for like a second. Something like an apple or a door. After a while, I was able to replay cartoon scenes in my head. And now, I can imagine any visual experience I want. Also, the one time I was able to get FILD working, I utilized visualization to steer the experience in my preferred direction.
Practicing visualization is easy, just try to imagine something. Anything. The more complex the scene or object, the harder it will be to imagine. Work your way up to moving objects and eventually to entire scenes. I found that just trying to replay an experience in my head works the best.