First of all, let's define what a flashback is: Although the term itself is fairly self-explanatory, a flashback is scene or series of scenes that shows a reader something that happened at a time before the present of a story being told.
Often, a writer wants to "set the stage" or background for the present story. He might then write of a time that happened days, months or years ago and do it in a dramatic and interesting way. The purpose of this is to let the reader know why characters are behaving in the way they are being portrayed, or how things came to be the way they are in the story's present.
For instance, why does Ravi not get along well with his father, who is a venerable and respected elder of the Order of the Ras Brotherhood? Why is Ras Rojo the only monk who does not command his son's respect? A short, but dramatic scene takes us back to a time when Ravi was a young boy and was left with his weeping, devastated mother, a princess of the Crystalline Court. She pleads pitifully, but Ravi's princeling father callously turns a deaf ear to her heart-rending entreaties to not join the Brotherhood and leave his only son fatherless.
A flashback shows "antecedent action" and sets the stage to bring the characters involved more depth and reality. Future relationships between the characters - and with the reader - might well be based on the antecedent action of a flashback.
A flashback may be done either in dramatic narrative or in dialogue between two or more characters, but its main purpose remains the same: to lay the base-work story so that the reader will know what's going on "behind the scenes" and will be able to recognize any future clues and/or foreshadowing that the writer may want to put forth.
Flashbacks should not be used just for the sake of usage. That is to say, don't stick one in just because you think it might be time to have one. A flashback should be used only to provide the reader with additional and possibly insightful information regarding your character or the plot, or both.
Care must be taken not to cause confusion, as well. Some tips to help avoid confusing the reader are as follows:
Remembrance triggers - a character "remembers" something that happened in the past by the evocation of an emotional trigger. The writer uses a sensory trigger, such as an aroma, a visual reminder, a sound or the touch of something in the present scene which causes your character's memory to kick in and transition to the past event.
Some examples might be, the smell of magnolias causing your character to remember a particular woman's perfume, the distant rumble and shriek of a train's whistle reminding him of a trip they took together, a young couple walking hand in hand, the brush of a soft breeze on his skin that reminds him of her silk scarf. Get the picture?
Present and past tense usage - for instance, the use of the verb "to have" and "had" as in, "Ravi remembered that his mother had been devastated." This is a simple, yet effective method to signal your reader almost automatically whether you are writing of the past, or of the present.
Explaining background - use a flashback to explain the "why" and the "how" of things as they came to be in the present. Other questions may be answered, as well, as the writer sees fit. This is an excellent method of dropping the reader a "secret clue" that no other character knows except the one involved and the reader himself.
For example, no one can understand why Ravi is so disrespectful to his father. Even to Ras Rojo's mind, his choice to leave wife and son may have been entirely justified. In this instance, a flashback reveals clues so that only the reader can identify with Ravi's internal pain. All other characters are oblivious and blame Ravi for being a bad son.
Above all, make sure to keep the chronology of the story straight as you transition from present to past and back to the present again. Over-use of flashbacks tends to confuse the issue and a confused reader will often give up and put the book down.
Try to use a flashback with finesse. Just as an artist uses a particularly fine brush to colour in the detail of his painting, words are a writer's paint box and the blank page is his palette. Use them wisely and you will paint a picture as beautiful and as colourful as any rendered by Van Gogh or Rembrandt.
