Are you just trying to act differently, or do you want to change your attitude altogether? If it is the latter, it will take years of discipline and hard work. Note I did not say change your personality.
Meditation is one route to take, but it is far from the only.
So let's say you're trying to stop acting out in anger, for example.
It can start with becoming aware of what exactly sets you off, how, and why. Remember: You cannot always change the circumstance, or even avoid it. But you can change how you react to it. Study yourself. Learn your own physical reactions -- from feeling the heat of blood in your face, to your clenching hands, to your accelerating heart beat; maybe it's more subtle, emotional reactions -- still pay close attention. Start looking out for those actions. Use them to come to a full stop with whatever you were doing or were about to do. Learn that as your next move rather than just going with it. I believe the same would apply even with things like doing some unkind thing to someone else. This is related to mindfulness -- that is one type of meditation to learn and practice. It is simply being aware of yourself, your emotions, etc.
Take time alone to re-hash situations for reexaminations. Figure out exactly why you react the way you do. Experience the emotion, but try to keep it external -- keep it in the memory of the experience, and do not allow it to affect you. This is another meditation exercise, related to visualization.
Continue this type of meditation exercise. Learn to separate that emotional response from feeling like a part of you. Emotions can be experienced, or they can be acknowledged and let go. "Yes: this is anger. I choose not to get angry."
There are other exercises which can be used in situations, and they can be either drawn out, or made brief.
Breathing exercises, for example: I like to do several different specific types. They vary from a pause to force myself to release, to a lengthy visualization of inhaling whatever I choose as what I want, and exhaling what I want to release. I choose a place to visualize, whether in the woods, atop a mountain, in the sky, or some abstract of outer space.
Another visualization I use is that of a stream or river. I am a stone in the water, which washes away, slowly eroding me. IT is not a bad thing; rather, it is nature, and very good. I can release into the water anything, no matter how easy or difficult. Eventually, I will become like nothing, but the water flows on. Sometimes emotions are difficult to let go, like grains of a stone. But given time, in the right environment, and the right intention, change happens.
Not to mention, it takes determination. It also requires being open with those close to you. Don't ask them to change; rather, tell them you're working on that aspect of yourself, and that it's alright to call you out on improper behavior.
It is not the only possible path, nor is it the best for everyone. So explore your options and see what works best for you.
Also: This is creating a change (an emotional one) to align with your will.