I used to do it years ago. I started because I was really depressed and couldn't think of ways to cope with the pain. First I started with tiny cuts, just using safety pins and the edge of scissors. As time went on, I moved onto exacto knives and other things that produced much deeper cuts.
I loved to watch myself bleed. It just soothed me and made my soul feel so much more complete. I did it on my arms, belly, chest, legs, wrists...just about everywhere, but only places I could cover up (tshirts, pants, wrist bands). I didn't want anybody to see because I was ashamed of it.
My father was an extreme alcoholic, so I did something kind of stupid. He was trying to recover, and I gave myself the mentality of "I will only cut when he drinks. When he fails his addiction, that means I can too".
Eventually I realized that his addiction should have nothing to do with mine, and just because he fails doesn't mean that I had to fail too. Time went on, and with the help of friends and family I started to do it less and less. My boyfriend ended up helping me to stop all together, and now I've been cut free for over a year. Sometimes I miss it, but my life is much better off without it. I used to be so bad to the point where I carried around an exacto knife with me in my wallet/purse everywhere I went. It's such a relief to know I can rely on other things to make me feel better.