In Great Expectations, the names employed by Dickens are significant because they help to convey his key ideas. Here are some examples:

• Pip - the word, Pip, means the seed of a fruit and, just like a seed, the novel deals primarily with Pip's growth and development from boy to man. Pip's name is, therefore, also symbolic of the novel as a bildungsroman (a coming-of-age story).
• Estella - derived from the Latin word for "star," Estella really has star-like qualities in the novel since she shines so brightly in Pip's opinion. Like a star, she is Pip's guide, his focus, and his sole interest for much of the novel. 
• Magwitch - the word "witch" in this name suggests something supernatural or otherworldly. In many ways, this is an accurate means of portraying Magwitch since he is an escaped criminal, living on the fringe of society, and representing the underbelly of Victorian society, a theme which Dickens often explores.

Dickens often uses symbolic names, but Great Expectations is probably the best example of his doing so.

Pip's name is, of course, the most symbolic.  His nickname means "seed," and the novel is about Pip's growth and maturity.  It is a Bildungsroman which is a work about the maturation of an individual.  Like a seed, Pip is "planted," and the reader witnesses his growth.

Miss Havisham's name is rather ambiguous.  One could interpret it to be "have a shame."  She was so shamed by being jilted that the weight of that shame alters her entire existence. More in keeping, however, with her vengeful nature is a second interpretation of "have a sham."  Miss Havisham puts on a sham by luring men toward Estella, raising their hopes, and then encouraging Estella to break their hearts.  She also allows Pip to believe the sham that she is his mysterious benefactress.

Estella's name in one of the most fitting.  "Stella" means "star."  Estella, like a star, is bright and beautiful.  Men love to gaze upon her, but she is untouchable.  As a star, she is cold and distant, and no one can get close enough to know her fully.

I hope this helps you with a few.  To figure out the symbolism of other names (not all of them are symbolic), don't hesitate to break the names into parts, consider allusions, or match up the meanings of stems and roots with the names.