Do you have bad habits you would like to stop, or good habits you would like to start? They are effectively the same task; both can be handled simply, but only if you put your mind to it. It's as easy and as difficult as that.
In my recent book, Tai Chi In Your Life, I discuss eight principles of Tai Chi Chuan (taijiquan) that you can productively incorporate into every aspect of your daily life. At the core, the book is about cultivating useful traits and, you might say, de-cultivating negative traits.
One early teacher I had put habit formation like this: ideas lead to actions; actions lead to habits; habits form character. That does not tell you how to cultivate new habits, but it tells you how why it is important to do so. Our habits define who we are.
In class, students are constantly gaining new insights into movement, which makes them want to reform their own movement to perform more correctly. But how? Where does the process begin and end?
It starts with relaxation, the first principle of Tai Chi; without relaxing, you can do nothing correctly. You can't even relax your mind enough to grasp the new reality presented to you.
Next comes awareness (third principle): awareness of the correct movement, of the mistake previously made, of the need to make correction.
Your awareness must extend to the point that you accept (seventh principle) it, and yield to the reality of what is needed. In order to accept it, you must detach your ego (eighth principle) to the point that you can overcome preconceived notions and accept newer, more valid, approaches.
Now the real work begins: applying the lesson to the creation of a new habit. As you train, you must be constantly (i.e., continuously, fourth principle) alert to situations arising that call for the correct new habit to be performed.
When you recognize the situation that calls for the new habit / improved movement, you must focus (fifth principle) clearly on the correct approach. Every time you do it correctly, you reinforce the new habit. Every time you miss and do it incorrectly, you are holding back on your potential.
You form the habit by keeping your awareness continuously alive and then focusing on the correct response. Translate your mental awareness into physical action. With training and experience, your habit will become more and more a part of you, until it is what you do without effort, like breathing.