Be aware that you may feel anger at the person, at the world, at family members or friends, at God, at yourself. Don't push down the anger. Hit a pillow, swim, exercise, hit a bunching bag, scream. You may feel guilty for what you think you did or did not do. Remember that very often there was nothing you could have done to control what happened.
Guilt is simply a natural part of the grieving process.
Don't be afraid to cry. Tears are healing. Don't be afraid to talk to the person who has died. Keep a journal. Don't be surprised by fear.