Change your Behavior. Dependency is expressed through dependent behavior. Working on changing your dependent behavior habits will go far towards decreasing your overall dependency.
There are several ways you can work directly on changing your dependent behavior habits.
You can study Assertiveness Training. Assertiveness training teaches the distinction between passive, aggressive and assertive forms of behavior. Most dependent behavior is passive in nature. Dependent people benefit from learning to act more assertively; to stand up for themselves, in a polite and respectful manner that does not cross the line into aggression. In addition to our discussion of Assertiveness (above in this document), you might also consider reading books about assertiveness, and/or participating in assertiveness workshops that might be offered by local area therapists. The classic book on assertiveness is, "Your Perfect Right" by Robert Alberti and Michael Emmons and published by Impact Press.
As you practice assertiveness skills, prepare yourself to deal with resistance on the part of family members, "friends" and co-workers who have a vested interest in the status quo, and don't particularly want you to change. When confronted by your newly assertive behavior, such people will typically escalate their own counter-behaviors in an effort to keep you down. They may accuse you of getting "uppity", remind you that you are incompetent, or even become abusive. Don't allow such responses to deter you from your assertive direction.
Sometimes dependent, passive behavior happens because people are afraid that if they assert themselves that something bad will occur. In many cases, a less emotional, more objective appraisal of the situation reveals that there is actually little to fear. If this description fits your own situation, you might consider creating a fear hierarchy and using an exposure method to desensitize yourself to those fears. You can do this using Graduated Exposure (e.g., in vivo - live exposure), or Systematic Desensitization (e.g., in vitro - imagined exposure) methods; whatever suits you best.
If you don't want a graduated approach to your exposure therapy, consider Prescriptive Risk Taking, instead. In prescriptive risk taking, you prescribe for yourself a task or two that you want to try out. The task should be one that frightens you to some reasonable degree, and which you would normally not take on but rather defer to someone else's expertise. The task might be changing your own oil, repairing your own leaky faucet, making dinner for yourself, respectfully sharing your ideas in a work situation, offering an opinion about where you want to go on vacation or anything of this sort. You set yourself the goal of performing this task on your own, and then you go out and do it. You may need to research how to do it before you dive in; that is not only okay - it is expected of you. Your successful completion of your task will help raise up your confidence. Even if you are unable to completely solve your task, you will have gained new knowledge you didn't have before about what doesn't work (grin!), and you should try again until you get it right.
You might even want to take a Relapse Prevention approach to dependency, once you start becoming more aware of the various ways you perpetuate the behavior. Recognize the triggering situations (people, places and things) that "push your buttons" and cause you to start feeling and acting dependent. Use this recognition to interrupt a chain of dependent behaviors and thoughts and substitute more positive, empowering thoughts and behaviors.