Well, the first step is wanting and being determined to stop. You can't say that you're just "addicted" and can't stop. No, you have to go into the techniques trying, and being ready to face the temptation of wanting to cut. But you have to be determined.
So, I know a few techniques that are pretty helpful. Really, if you feel like you want to cut, just talk to someone. I have an older cousin that I call if I need to talk.
Anyway, as for techniques (this is going to be extremely long, sorry in advance)...
1 -- The rubber band technique. This one is simple... just wear a rubber band around your wrist. Whenever you think you need physical pain, pull it and release it so that it snaps against your skin.
2 -- The butterfly technique. I actually really like this one, even though it sounds kind of odd... Draw a butterfly on your hand, and name it after someone you know and love. If you cut yourself before that butterfly fades, you've killed the person that you named it after.
3 -- The marker technique. This is another one that I enjoy. Just taking a red marker and marking your skin. You can press as hard as you want, and act as if this is something real. It actually kind of just gives me a thirst for the whole cutting thing, but it makes me quite happy to do. I mean, you can do it as savagely as you want without anyone having to watch..just take your stress out on yourself in a healthier way... I suppose I definitely recommend doing this one pre-shower. I occasionally take one into the bathroom with me, and go through the process of marker-ing myself right before I shower. It's pretty nice.
4 -- This one is rather similar to the marker technique. I usually save tags after buying something... like price tags or brand name tags...you know? So, putting those against your skin and slicing with them definitely is relieving to me. It really doesn't do anything (unless you pick an oddly sharp and jagged tag, which I don't recommend), but it feels pretty great. I usually don't use the corners, but just put the tag flat against my skin and swipe. I also love using red-ish or pink-ish eye shadow or blush. You can use an eye shadow tool sideways and slice with them... it makes a satisfying color, while also feeling of it moving across your skin.
I'm also a huge fan of writing instead. I mean, sure it sounds depressing and lonely, but is that not what I'm feeling inside? It's almost just as relieving to have your feelings on paper...so you can actually try to understand the complex feelings that you're going through. Sometimes I write to specific people (usually people that I feel are "ignoring" me, so I kind of just "tell" them are I feel about that and endless people-would-think-I'm-crazy kind of stuff).
Also, weening yourself off of cutting IS possible. Just try to resist, just once. It will get easier. I find it quite helpful... just to limit myself. Sometimes I can become angry I'm not satisfied with the depth or length of the cut (I'm so weird, sometimes I prefer short deep ones which are just really hard to do, and I continuously try until I can't control all of the bleeding)... but I've learned to be consciously aware of this... I mostly just FORCE myself not to do more. One to a few is just enough. When you've mastered that, try completely resisting once. Just wait until the next day, that's all. When you make it to the next day, go right ahead if you feel like you must. Control the depth, don't go too deep.
Best of luck! I hope you can conquer this. :)
Edit -- One more thing that my aunt introduced me to, and I find it unbelievably helpful.
You're supposed to find something pleasant for each one of your senses.
Like sight. Look at a picture of someone you care about (or something you care about, like if you have a pet). Save notes that someone special writes to you, print out the emails they send and read those, whatever it takes...
Or for scent, smell some sort of perfume that reminds you of someone... or smell some certain food.. This might seem silly, but I seriously do have a shirt that I haven't worn in over a year simply because it smells like my cousin's house. And I adore that. Smell is most distinctly linked with memory, and it's definitely the most helpful one. Or you can even just spray some piece of cloth with a scent that reminds you of something pleasant. Or you can go outside, smell the outdoors of that helps. I also actually had to get 17 sterie strips (they're an alternative to stitches) while I was at my cousins a few months ago. They have this absolutely GROSS smelling stuff that you spread around the cuts to help the strips stick and stay there. I somehow grew to love that scent, just because it reminds me of being there...
Touch -- This is a hard one. I've tried to hug stuffed animals or blankets, and all of that usually just makes me feel more alone. My aunt actually gave me a little glass heart, and I hold that thing all the time. If you can hold those letters or notes they may have written to you, hold something that was a gift, hold someONE even, that would be great. If all fails...hold yourself. It doesn't have to be something dumb, just be in private, at night, in your bed, comfort yourself. Sure it sounds dumb, but I actually find it helpful to fantasize about what it would be like to be helped, fantasize about what it would be like to have that person that cares (even if they have to be a made-up person) here, and what I would tell them (even though I really wouldn't tell them much, I'm pretty chicken when it comes to talking), and what they might say back. Sometimes I hold my own hand, because my cousin would always hold my hand when I was there, and it reminds me of her. I'd squeeze my own hand 3 times because that's something we did there. First for "I" second for "love" and third for "you".
Taste -- Chocolate seriously does release endorphins. Just like cutting. My cousin gave me the idea of keeping "emergency chocolate" somewhere where I can always get it. She made me a little cardboard box (which said "emergency chocolate" on it) that could hold a candy bar or something. Or just eat something you enjoy, calm those taste buds. ;) Don't be concerned about the fattening qualities, you can walk those off. You don't need to eat A LOT of something, maybe just a bit of chocolate, a little ice cream, maybe you can melt string cheese in the microwave for 12 seconds (yum!).... anything you enjoy eating.
Hearing -- Listen to music. I ADORE Owl City, if you need something to listen to. And Copeland (the newest CDs of both of these people are best, but really, I love all of Owl City's songs). If someone has left a voicemail on your phone that you appreciated, listen to that. Record it (I actually record a video of it, then record the sound of that video back on to my phone), and play it whenever you need to hear that person's voice. Or, better yet, just CALL that person. :) I love talking to people on the phone, and I've always found that quite helpful.
I hope this helps you, don't give up.