eHow has a good, practical rundown of tips you can use to comfort someone in your life who is grieving:
Allow the person to talk about his grief and express his feelings. Listen without offering advice or interrupting.
Give the person as much time as he needs to grieve. Telling him to 'get over it' or 'let it go' won't help him grieve any faster.
There is no 'correct' amount of time to mourn a loss. The grieving period varies with the individual.
Be sensitive to significant dates such as birthdays, holidays and the anniversary of the death or loss; the grieving person may find these especially difficult times.
How to Comfort a Grieving Person [Source: Lifehacker]
Allow the person to talk about his grief and express his feelings. Listen without offering advice or interrupting.
Give the person as much time as he needs to grieve. Telling him to 'get over it' or 'let it go' won't help him grieve any faster.
There is no 'correct' amount of time to mourn a loss. The grieving period varies with the individual.
Be sensitive to significant dates such as birthdays, holidays and the anniversary of the death or loss; the grieving person may find these especially difficult times.
How to Comfort a Grieving Person [Source: Lifehacker]