It can take the form of amnesia. I had no memory of what happened at the time when some of the trauma and betrayal stuff happened for years afterward. When it came back I was overwhelmed with flashbacks and stuff, so splitting was an attempt to protect myself from that I guess. I would not be able to remember what day it was or how long ago the flashbacks were either, so I guess that was dissociation too. It can also take the form of splitting from one's body, maybe flying around the room, or detaching and looking down on the scene from above. Sometimes different personalities form during splitting. This gets called multiple personality disorder or dissociative identity disorder (DID).
Addictions often have a component of splitting. Addictive behavior, whether in the consumption of a drug, obsessive or compulsive sex, gambling, or even religious or artistic preoccupation, can be a form of splitting, of creating a fantasy reality that ignores the real state of things. Lots of addicts talk about a "Jekyll and Hyde" experience of having one set of values and behaviors they believe in and another personality, the out of control addict, that seems intent on destroying these.
Some signs of dissociation are spacing out as a response to painful memories, confusion and forgetfulness because of preoccupation, resorting to a fantasy world when things get tough, feeling separate from the body as the result of a flashback, amnesia, preoccupation, having compartments to your life others don't know about, living a double life, obsessing around addictive behavior, losing yourself in romantic fantasies, or using marijuana or psychedelic drugs. All of us space out sometimes, the problem is when it becomes a way of life.
All the quotations and information not otherwise attributed above comes from Patrick J. Carnes, The Betrayal Bond: Breaking Free of Exploitive Relationships (Deerfield Beach, Fla.: Health Communications Inc., 1997), 14-17.